# Enzo Parameter List¶

The following is a largely complete list of the parameters that Enzo understands, and a brief description of what they mean. They are grouped roughly by meaning; an alphabetical list is also available. Parameters for individual test problems are also listed here.

This parameter list has two purposes. The first is to describe and explain the parameters that can be put into the initial parameter file that begins a run. The second is to provide a comprehensive list of all parameters that the code uses, including those that go into an output file (which contains a complete list of all parameters), so that users can better understand these output files.

The parameters fall into a number of categories:

external
These are user parameters in the sense that they can be set in the parameter file, and provide the primary means of communication between Enzo and the user.
internal
These are mostly not set in the parameter file (although strictly speaking they can be) and are generally used for program to communicate with itself (via the restart of output files).
obsolete
No longer used.
reserved
To be used later.

Generally the external parameters are the only ones that are modified or set, but the internal parameters can provide useful information and can sometimes be modified so I list them here as well. Some parameters are true/false or on/off boolean flags. Eventually, these may be parsed, but in the meantime, we use the common convention of 0 meaning false or off and 1 for true or on.

## Initialization Parameters¶

TopGridRank (external)
This specifies the dimensionality of the root grid and by extension the entire hierarchy. It should be 1,2 or 3. Default: none
TopGridDimensions (external)
This is the dimension of the top or root grid. It should consist of 1, 2 or 3 integers separated by spaces. For those familiar with the KRONOS or ZEUS method of specifying dimensions, these values do not include ghost or boundary zones. A dimension cannot be less than 3 zones wide and more than MAX_ANY_SINGLE_DIRECTION - NumberOfGhostZones*2. MAX_ANY_SINGLE_DIRECTION is defined in fortran.def. Default: none
DomainLeftEdge, DomainRightEdge (external)
These float values specify the two corners of the problem domain (in code units). The defaults are: 0 0 0 for the left edge and 1 1 1 for the right edge.
LeftFaceBoundaryCondition, RightFaceBoundaryCondition (external)
These two parameters each consist of vectors of integers (of length TopGridRank). They specify the boundary conditions for the top grid (and hence the entire hierarchy). The first integer corresponds to the x-direction, the second to the y-direction and the third, the z-direction. The possible values are: 0 - reflecting, 1 - outflow, 2 - inflow, 3 - periodic, 4 - shearing. For inflow, the inflow values can be set through the next parameter, or more commonly are controlled by problem-specific code triggered by the ProblemType. For shearing boundaries, the boundary pair in another direction must be periodic. Note that self gravity will not be consistent with shearing boundary conditions. Default: 0 0 0
BoundaryConditionName (external)
While the above parameters provide an easy way to set an entire side of grid to a given boundary value, the possibility exists to set the boundary conditions on an individual cell basis. This is most often done with problem specific code, but it can also be set by specifying a file which contains the information in the appropriate format. This is too involved to go into here. Default: none
StoreDomainBoundaryMassFlux (external)
When turned on, this stores the cumulative mass (in solar masses) of density fields (density, species fields, metallicity) that outflows from the simulation domain. This is stored directly in the output parameter files as the BoundaryMassFluxFieldNumbers and BoundaryMassFluxContainer parameters, as well as the cycle-by-cycle mass outflow in BoundaryMassFluxFilename. Default : 0 (off)
BoundaryMassFluxFilename (external)
The filename to output the cycle-by-cyle mass outflow from the grid domain when the above parameter is ON. Default : ‘boundary_mass_flux.dat’
InitialTime (internal)
The time, in code units, of the current step. For cosmology the units are in free-fall times at the initial epoch (see Enzo Output Formats). Default: generally 0, depending on problem
Initialdt (internal)
The timestep, in code units, for the current step. For cosmology the units are in free-fall times at the initial epoch (see Enzo Output Formats). Default: generally 0, depending on problem
Unigrid (external)
This parameter should be set to 1 (TRUE) for large cases–AMR as well as non-AMR–where the root grid is 5123 or larger. This prevents initialization under subgrids at start up, which is unnecessary in cases with simple non-nested initial conditions. Unigrid must be set to 0 (FALSE) for cases with nested initial conditions. Default: 0 (FALSE). See also ParallelRootGridIO in I/O Parameters.
UnigridTranspose (external)
This parameter governs the fast FFT bookkeeping for Unigrid runs. Does not work with isolated gravity. Option 0 is the slowest of the methods. Option 1 is an aggressive version that is memory-intensive. Option 2 tries to conserve memory at the expense of performance. See also Unigrid above. Default: 2.
MaximumTopGridTimeStep (external)
This parameter limits the maximum timestep on the root grid. Default: huge_number.
ShearingVelocityDirection (external)
Select direction of shearing boundary. Default is x direction. Changing this is probably not a good idea.
AngularVelocity (external)
The value of the angular velocity in the shearing boundary. Default: 0.001
VelocityGradient (external)
The value of the per code length gradient in the angular velocity in the shearing boundary. Default: 1.0
GridVelocity (external)
The whole computational domain will have this velocity. Experimental. Default: 0 0 0
StringKick (external)
While this parameter was initially designed to describe the kick by cosmic strings in CosmologySimulation, it can be used to model the velocity (in km/s) that the baryons should move relative to dark matter at the initial redshift, in order to study the effect discussed by Tseliakhovich & Hirata (astro-ph:1005.2416). Default: 0
StringKickDimension (external)
This parameter is used to control the orthogonal direction of the flow. Default: 0 (x-axis)
MemoryLimit (external)
If the memory usage on a single MPI process exceeds this number, then the simulation will halt after outputting. Only used when the compile-time define MEM_TRACE is used. Default: 4e9
HydrogenFractionByMass (external)
This parameter is used to set up initial conditions in some test problems. Default: 0.76
DeuteriumToHydrogenRatio (external)
This parameter is used to set up initial conditions in some test problems. Default: 2.0*3.4e-5 (Burles & Tytler 1998, the parameter here is by mass, so multiply by 2)
SolarMetalFractionByMass (external)
This parameter is used to set up initial conditions in some test problems. Do NOT change this parameter unless you know exactly what you are doing. Default: 0.02041
CoolDataIh2co (external)
Whether to include molecular hydrogen cooling. Do NOT change this parameter unless you know exactly what you are doing. Default: 1
CoolDataIpiht (external)
Whether to include photoionization heating. Do NOT change this parameter unless you know exactly what you are doing. Default: 1
CoolDataCompXray (external)
Do NOT change this parameter unless you know exactly what you are doing. Saved to CoolData.comp_xray. Default: 0
CoolDataTempXray (external)
Do NOT change this parameter unless you know exactly what you are doing. Saved to CoolData.temp_xray. Default: 0
NumberOfTemperatureBins (external)
Do NOT change this parameter unless you know exactly what you are doing. Default: 600
TemperatureStart (external)
Do NOT change this parameter unless you know exactly what you are doing. Default: 10
TemperatureEnd (external)
Do NOT change this parameter unless you know exactly what you are doing. Default: 1e8
ExternalBoundaryIO (external)
not recommended for use at this point. Only works if compiled with ooc-boundary-yes. Default: 0
ExternalBoundaryTypeIO (external)
not recommended for use at this point. Default: 0
ExternalBoundaryValueIO (external)
not recommended for use at this point. Default: 0
SimpleConstantBoundary (external)
not recommended for use at this point. Default: 0

## I/O Parameters¶

### General I/O Parameters¶

There are three ways to specify the frequency of outputs: time-based, cycle-based (a cycle is a top-grid timestep), and, for cosmology simulations, redshift-based. There is also a shortened output format intended for visualization (movie format). Please have a look at Controlling Enzo Data Output for more information.

dtDataDump (external)
The time interval, in code units, between time-based outputs. A value of 0 turns off the time-based outputs. Default: 0
dtInterpolatedDataDump (external)
The time interval, in code units, between time-based interpolated outputs. A value of 0 turns off the time-based outputs. Default: 0
CycleSkipDataDump (external)
The number of cycles (top grid timesteps) between cycle-based outputs. Zero turns off the cycle-based outputs. Default: 0
SubcycleSkipDataDump (external)
The number of subcycles between subcycle-based outputs. Zero turns off the subcycle-based outputs. Default: 0
dtTracerParticleDump (external)
The time interval, in code units, between time-based tracer particle outputs (defined in ComputeRandomForcingNormalization.C). A value of 0 turns off this output. Default: 0
DataDumpName (external)
The base file name used for both time and cycle based outputs. Default: data
RedshiftDumpName (external)
The base file name used for redshift-based outputs (this can be overridden by the CosmologyOutputRedshiftName parameter). Normally a four digit identification number is appended to the end of this name, starting from 0000 and incrementing by one for every output. This can be over-ridden by including four consecutive R’s in the name (e.g. RedshiftRRRR) in which case an identification number will not be appended but the four R’s will be converted to a redshift with an implied decimal point in the middle (i.e. z=1.24 becomes 0124). Default: RedshiftOutput
TracerParticleDumpName (external)
The base file name used for tracer particle outputs. Default:
TracerParticleDumpDir (external)
The dir name used for tracer particle outputs. Default:
dtRestartDump
Reserved for future use.
dtHistoryDump
Reserved for future use.
CycleSkipRestartDump
Reserved for future use.
CycleSkipHistoryDump
Reserved for future use.
RestartDumpName
Reserved for future use.
HistoryDumpName
Reserved for future use.
CosmologyOutputRedshift[NNNN] (external)
The time and cycle-based outputs occur regularly at constant intervals, but the redshift outputs are specified individually. This is done by the use of this statement, which sets the output redshift for a specific identification number (this integer is between 0000 and 9999 and is used in forming the name). So the statement CosmologyOutputRedshift[1] = 4.0 will cause an output to be written out at z=4 with the name RedshiftOutput0001 (unless the base name is changed either with the previous parameter or the next one). This parameter can be repeated with different values for the number (NNNN) Default: none
CosmologyOutputRedshiftName[NNNN] (external)
This parameter overrides the parameter RedshiftOutputName for this (only only this) redshift output. Can be used repeatedly in the same manner as the previous parameter. Default: none
FileDirectedOutput
If this parameter is set to 1, whenever the finest level has finished evolving Enzo will check for new signal files to output. (See Force Output Now.) Default 1.
TracerParticleOn
This parameter is used to set the velocities of the tracer particles equal to the gas velocities in the current cells. Tracer particles are massless and can be used to output values of the gas as they advect with the fluid. Default: 0
TracerParticleOutputVelocity
This parameter is used to output tracer particle velocity as well as position, density, and temperature. Default: 0
OutputFirstTimeAtLevel (external)
This forces Enzo to output when a given level is reached, and at every level thereafter. Default is 0 (off). User can usefully specify anything up to the maximum number of levels in a given simulation.
ParallelRootGridIO (external)
Normally for the mpi version, the root grid is read into the root processor and then partitioned to separate processors using communication. However, for very large root grids (e.g. 5123), the root processor may not have enough memory. If this toggle switch is set on (i.e. to the value 1), then each processor reads its own section of the root grid. More I/O is required (to split up the grids and particles), but it is more balanced in terms of memory. ParallelRootGridIO and ParallelParticleIO MUST be set to 1 (TRUE) for runs involving > 64 cpus! Default: 0 (FALSE). See ParallelParticleIO in Particle Parameters. See also Unigrid in Initialization Parameters.
OutputTemperature (external)
Set to 1 if you want to output a temperature field in the datasets. Always 1 for cosmology simulations. Default: 0.
OutputCoolingTime (external)
Set to 1 if you want to output the cooling time in the datasets. Default: 0.
OutputSmoothedDarkMatter (external)
Set to 1 if you want to output a dark matter density field, smoothed by an SPH kernel. Set to 2 to also output smoothed dark matter velocities and velocity dispersion. Set to 0 to turn off. Default: 0.
SmoothedDarkMatterNeighbors (external)
Number of nearest neighbors to smooth dark matter quantities over. Default: 32.
OutputGriddedStarParticle (external)
Set to 1 or 2 to write out star particle data gridded onto mesh. This will be useful e.g. if you have lots of star particles in a galactic scale simulation. 1 will output just star_particle_density; and 2 will dump actively_forming_stellar_mass_density, SFR_density, etc. Default: 0.
PopIIIOutputOnFeedback (external)
Writes an interpolated output when a Pop III is formed or goes supernova. Default: 0
OutputOnDensity (external)
Should interpolated outputs be generated at varying peak density? Default: 0
StartDensityOutput (external)
The first density (in log g/cc) at which to output.
CurrentDensityOutput (internal)
The most recent density at which output was generated.
IncrementDensityOutput (external)
After a density-directed output, how much should the density be increased by? Default: 999
ComputePotential (external)
When turned on, the gravitational potential is computed and stored in memory. Always done when SelfGravity is on. Default: 0
WritePotential (external)
When turned on, the gravitational potential is written to file. Default: 0
WriteGhostZones (external)
Should ghost zones be written to disk? Default: 0
ReadGhostZones (external)
Are ghost zones present in the files on disk? Default: 0
VelAnyl (external)
Set to 1 if you want to output the divergence and vorticity of velocity. Works in 2D and 3D.
BAnyl (external)
Set to 1 if you want to output the divergence and vorticity of Bfield. Works in 2D and 3D.
ExtractFieldsOnly (external)
Used for extractions (enzo -x …) when only field data are needed instead of field + particle data. Default is 1 (TRUE).
XrayLowerCutoffkeV, XrayUpperCutoffkeV, XrayTableFileName (external)
These parameters are used in 2D projections (enzo -p ...). The first two specify the X-ray band (observed at z=0) to be used, and the last gives the name of an ascii file that contains the X-ray spectral information. A gzipped version of this file good for bands within the 0.1 - 20 keV range is provided in the distribution in input/lookup_metal0.3.data. If these parameters are specified, then the second field is replaced with integrated emissivity along the line of sight in units of 10-23 erg/cm2/s. Default: XrayLowerCutoffkeV = 0.5, XrayUpperCutoffkeV = 2.5.
ParticleTypeInFile (external)
Output ParticleType to disk? Default: 1
OutputParticleTypeGrouping (external)
In the grid HDF5 groups, particles are sorted by type, and a reference is created to indicate which particle index range corresponds to each type. Default: 0
HierarchyFileInputFormat (external)
See Controlling the Hierarchy File Output Format.
HierarchyFileOutputFormat (external)
See Controlling the Hierarchy File Output Format.
TimingCycleSkip (external)
Controls how many cycles to skip when timing information is collected, reduced, and written out to performance.out. Default: 1
DatabaseLocation (external)
(Not recommended for use at this point) Where should the SQLite database of outputs be placed?
CubeDumpEnabled (external)
not recommended for use at this point. Default: 0
CubeDump[] (external)
not recommended for use at this point
LocalDir (external)
See Controlling Enzo Data Output.
GlobalDir (external)
See Controlling Enzo Data Output.

### Stopping Parameters¶

StopTime (external)
This parameter specifies the time (in code units) when the calculation will halt. For cosmology simulations, this variable is automatically set by CosmologyFinalRedshift. No default.
StopCycle (external)
The cycle (top grid timestep) at which the calculation stops. A value of zero indicates that this criterion is not be used. Default: 100,000
StopFirstTimeAtLevel (external)
Causes the simulation to immediately stop when a specified level is reached. Default value 0 (off), possible values are levels 1 through maximum number of levels in a given simulation.
StopFirstTimeAtDensity (external)
Causes the simulation to immediately stop when the maximum gas density reaches this value. In units of proper g/cm^3. Not used if less than or equal to zero. Default: 0.0
StopFirstTimeAtMetalEnrichedDensity (external)
Causes the simulation to immediately stop when the maximum gas density with above some metallicity, specified by EnrichedMetalFraction, is reached. In units of g/cm^3. Not used if less than or equal to zero. Default: 0.0
EnrichedMetalFraction (external)
See StopFirstTimeAtMetalEnrichedDensity. In units of absolute metal fraction. Default: 1e-8
NumberOfOutputsBeforeExit (external)
After this many datadumps have been written, the code will exit. If set to 0 (default), this option will not be used. Default: 0.
StopCPUTime (external)
Causes the simulation to stop if the wall time exceeds StopCPUTime. The simulation will output if the wall time after the next top-level timestep will exceed StopCPUTime, assuming that the wall time elapsed during a top-level timestep the same as the previous timestep. In units of seconds. Default: 2.592e6 (30 days)
ResubmitOn (external)
If set to 1, the simulation will stop if the wall time will exceed StopCPUTime within the next top-level timestep and run a shell script defined in ResubmitCommand that should resubmit the job for the user. Default: 0.
ResubmitCommand (external)
Filename of a shell script that creates a queuing (e.g. PBS) script from two arguments, the number of processors and parameter file. This script is run by the root processor when stopping with ResubmitOn. An example script can be found in input/resubmit.sh. Default: (null)

### Streaming Data Format¶

NewMovieLeftEdge, NewMovieRightEdge (external)
These two parameters control the region for which the streaming data are written. Default: DomainLeftEdge and DomainRightEdge.
MovieSkipTimestep (external)
Controls how many timesteps on a level are skipped between outputs in the streaming data. Streaming format is off if this equals INT_UNDEFINED. Default: INT_UNDEFINED
Movie3DVolume (external)
Set to 1 to write streaming data as 3-D arrays. This should always be set to 1 if using the streaming format. A previous version had 2D maximum intensity projections, which now defunct. Default: 0.
MovieVertexCentered (external)
Set to 1 to write the streaming data interpolated to vertices. Set to 0 for cell-centered data. Default: 0.
NewMovieDumpNumber (internal)
Counter for streaming data files. This should equal the cycle number.
MovieTimestepCounter (internal)
Timestep counter for the streaming data files.
MovieDataField (external)
A maximum of 6 data fields can be written in the streaming format. The data fields are specified by the array element of BaryonField, i.e. 0 = Density, 7 = HII Density. For writing temperature, a special value of 1000 is used. This should be improved to be more transparent in which fields will be written. Any element that equals INT_UNDEFINED indicates no field will be written. Default: INT_UNDEFINED x 6
NewMovieParticleOn (external)
Set to 1 to write all particles in the grids. Set to 2 to write ONLY particles that aren’t dark matter, e.g. stars. Set to 3/4 to write ONLY particles that aren’t dark matter into a file separate from the grid info. (For example, MoviePackParticle_P000.hdf5, etc. will be the file name; this will be very helpful in speeding up the access to the star particle data, especially for the visualization or for the star particle. See AMRH5writer.C) Set to 0 for no particle output. Default: 0.

### Simulation Identifiers and UUIDs¶

These parameters help to track, identify and group datasets. For reference, Universally Unique Identifiers (UUIDs) are opaque identifiers using random 128-bit numbers, with an extremely low chance of collision. (See Simulation Names and Identifiers for a longer description of these parameters.)

MetaDataIdentifier (external)
This is a character string without spaces (specifically, something that can be picked by “%s”), that can be defined in a parameter file, and will be written out in every following output, if it is found.
MetaDataSimulationUUID (internal)
A UUID that will be written out in all of the following outputs. Like MetaDataIdentifier, an existing UUID will be kept, but if one is not found, and new one will be generated.
MetaDataDatasetUUID (internal)
A UUID created for each specific output.
MetaDataRestartDatasetUUID (internal)
If a MetaDataDatasetUUID UUID is found when the parameter file is read in, it will written to the following datasets. This is used to track simulations across restarts and parameter adjustments.
MetaDataInitialConditionsUUID (internal)
This is similar to MetaDataRestartDatasetUUID, except it’s used to track which initial conditions were used.

## Hierarchy Control Parameters¶

StaticHierarchy (external)
A flag which indicates if the hierarchy is static (1) or dynamic (0). In other words, a value of 1 takes the A out of AMR. Default: 1
RefineBy (external)
This is the refinement factor between a grid and its subgrid. For cosmology simulations, we have found a ratio of 2 to be most useful. Default: 4
MaximumRefinementLevel (external)
This is the lowest (most refined) depth that the code will produce. It is zero based, so the total number of levels (including the root grid) is one more than this value. Default: 2
CellFlaggingMethod (external)

The method(s) used to specify when a cell should be refined. This is a list of integers, up to 9, as described by the following table. The methods combine in an “OR” fashion: if any of them indicate that a cell should be refined, then it is flagged. For cosmology simulations, methods 2 and 4 are probably most useful. Note that some methods have additional parameters which are described below. For more information about specific methods, see the method paper. Default: 1

CellFlaggingMethod Description
1 Refine by slope
2 Refine by baryon mass
3 Refine by shocks
4 Refine by particle mass
5 Refine by baryon overdensity
6 Refine by Jeans length
7 Refine if (cooling time < cell width/sound speed)
8 Refine by must-refine particles
9 Refine by shear
10 Refine by optical depth (in RT calculation)
11 Refine by resistive length (in MHD calculation)
12 Refine by defined region “MustRefineRegion”
13 Refine by metallicity
14 Refine by shockwaves (found w/shock finder)
15 Refine by normalized second derivative
16 Refine by Jeans length from the inertial tensor
19 Refine by metal mass
100 Avoid refinement based on ForbiddenRefinement field
101 Avoid refinement in regions defined in “AvoidRefineRegion”
RefineRegionLeftEdge, RefineRegionRightEdge (external)
These two parameters control the region in which refinement is permitted. Each is a vector of floats (of length given by the problem rank) and they specify the two corners of a volume. Default: set equal to DomainLeftEdge and DomainRightEdge.
RefineRegionAutoAdjust (external)
This is useful for multiresolution simulations with particles in which the particles have varying mass. Set to 1 to automatically adjust the refine region at root grid timesteps to only contain high-resolution particles. This makes sure that the fine regions do not contain more massive particles which may lead to small particles orbiting them or other undesired outcomes. Setting to any integer (for example, 3) will make AdjustRefineRegion to work at (RefineRegionAutoAdjust-1)th level timesteps because sometimes the heavy particles are coming into the fine regions too fast that you need more frequent protection. Default: 0.
RefineRegionTimeType (external)
If set, this controls how the first column of a refinement region evolution file (see below) is interpreted, 0 for code time, 1 for redshift. Default: -1, which is equivalent to ‘off’.
RefineRegionFile (external)

The name of a text file containing the corners of the time-evolving refinement region. The lines in the file change the values of RefineRegionLeft/RightEdge during the course of the simulation, and the lines are ordered in the file from early times to late times. The first column of data is the time index (in code units or redshift, see the parameter above) for the next six columns, which are the values of RefineRegionLeft/RightEdge. For example, this might be two lines from the text file when time is indexed by redshift:

0.60 0.530 0.612 0.185 0.591 0.667 0.208
0.55 0.520 0.607 0.181 0.584 0.653 0.201


In this case, the refinement region stays at the z=0.60 value until z=0.55, when the box moves slightly closer to the (0,0,0) corner. There is a maximum of 300 lines in the file and there is no comment header line. Default: None.

MinimumOverDensityForRefinement (external)

These float values (up to 9) are used if the CellFlaggingMethod is 2, 4 or 5. For method 2 and 4, the value is the density (baryon or particle), in code units, above which refinement occurs. When using method 5, it becomes rho [code] - 1. The elements in this array must match those in CellFlaggingMethod. Therefore, if CellFlaggingMethod = 1 4 9 10, MinimumOverDensityForRefinement = 0 8.0 0 0.

In practice, this value is converted into a mass by multiplying it by the volume of the top grid cell. The result is then stored in the next parameter (unless that is set directly in which case this parameter is ignored), and this defines the mass resolution of the simulation. Note that the volume is of a top grid cell, so if you are doing a multi-grid initialization, you must divide this number by r(d*l) where r is the refinement factor, d is the dimensionality and l is the (zero-based) lowest level. For example, for a two grid cosmology setup where a cell should be refined whenever the mass exceeds 4 times the mean density of the subgrid, this value should be 4 / (2(3*1)) = 4 / 8 = 0.5. Keep in mind that this parameter has no effect if it is changed in a restart output; if you want to change the refinement mid-run you will have to modify the next parameter. Up to 9 numbers may be specified here, each corresponding to the respective CellFlaggingMethod. Default: 1.5

MinimumMassForRefinement (internal)
This float is usually set by the parameter above and so is labeled internal, but it can be set by hand. For non-cosmological simulations, it can be the easier refinement criteria to specify. It is the mass above which a refinement occurs if the CellFlaggingMethod is appropriately set. For cosmological simulations, it is specified in units such that the entire mass in the computational volume is 1.0, otherwise it is in code units. There are 9 numbers here again, as per the above parameter. Default: none
MinimumMassForRefinementLevelExponent (external).
This parameter modifies the behaviour of the above parameter. As it stands, the refinement based on the MinimumMassForRefinement (hereafter Mmin) parameter is complete Lagrangian. However, this can be modified. The actual mass used is Mmin*r(l*alpha) where r is the refinement factor, l is the level and alpha is the value of this parameter (MinimumMassForRefinementLevelExponent). Therefore a negative value makes the refinement super-Lagrangian, while positive values are sub-Lagrangian. There are up to 9 values specified here, as per the above two parameters. Default: 0.0
SlopeFlaggingFields (external)
If CellFlaggingMethod is 1, and you only want to refine on the slopes of certain fields then you can enter the Field Type IDs of the fields you want, separating the IDs with a space. Up to 7 Field Type IDs can be specified. Default: Refine on slopes of all fields.
MinimumSlopeForRefinement (external)
If CellFlaggingMethod is 1, then local gradients are used as the refinement criteria. All variables are examined and the relative slope is computed: abs(q(i+1)-q(i-1))/q(i). Where this value exceeds this parameter, the cell is marked for refinement. This causes problems if q(i) is near zero. This is a single integer (as opposed to the list of five for the above parameters). Entering multiple numbers here correspond to the fields listed in SlopeFlaggingFields. Default: 0.3
MinimumPressureJumpForRefinement (external)
If refinement is done by shocks, then this is the minimum (relative) pressure jump in one-dimension to qualify for a shock. The definition is rather standard (see Colella and Woodward’s PPM paper for example) Default: 0.33
MinimumEnergyRatioForRefinement (external)
For the dual energy formalism, and cell flagging by shock-detection, this is an extra filter which removes weak shocks (or noise in the dual energy fields) from triggering the shock detection. Default: 0.1
MinimumShearForRefinement (external)
It is the minimum shear above which a refinement occurs if the CellFlaggingMethod is appropriately set. Default: 0
OldShearMethod (external)
If using the shear refinement criterion, setting this variable to 1 enables the old method for calculating the shear criterion, which actually calculates it based on shear and vorticity and makes some assumptions about the simulations (c_s=1, etc.). However, this is necessary if you want to reproduce some of the old enzo results (e.g. Kritsuk et al. 2006). Default: 0
MetallicityRefinementMinMetallicity (external)
For method 13 (metallicity refinement), this is the threshold metallicity (in units of solar metallicity) above which cells must be refined to a minimum level of MetallicityRefinementMinLevel. For method 19 (metal mass), this flags cells for refinement when the metal mass is above the necessary baryon mass (method 2) for refinement multiplied by this parameter. Behaves similarly to refinement by baryon mass but focuses on metal-enriched regions. In units of solar metallicity. Default: 1.0e-5
MetallicityRefinementMinLevel (external)
Sets the minimum level (maximum cell size) to which a cell enriched with metal above a level set by MetallicityRefinementMinMetallicity will be refined. This can be set to any level up to and including MaximumRefinementLevel. (No default setting)
MetallicityRefinementMinDensity (external)
It is the minimum density above which a refinement occurs when the cells are refined on metallicity. Default: FLOAT_UNDEFINED
ShockwaveRefinementMinMach (external)
The minimum Mach number required to refine a level when using ShockwaveRefinement. Default: 1.3
ShockwaveRefinementMinVelocity (external)
The minimum shock velocity required to refine a level when using ShockwaveRefinement. Default: 1.0e7 (cm/s)
ShockwaveRefinementMaxLevel (external)
The maximum level to refine to using the ShockwaveRefinement criteria. Default: 0 (not used)
SecondDerivativeFlaggingFields (external)
The field indices (list of up to 7) that are used for the normalized second derivative refinement criteria. Default: INT_UNDEFINED
MinimumSecondDerivativeForRefinement (external)
The value of the second derivative above which a cell will be flagged for refinement. Each value in this list (of up to 7 values) should be between 0.0 and 1.0. Values between 0.3-0.8 are recommended. Default: 0.3
SecondDerivativeEpsilon (external)
Used to avoid refining around oscillations/fluctuations in the normalized second derivative refinement method. The higher the value, the more it will filter out. For fluid instability simulations, a value of ~0.01 is good. For full-physics simulations, values around ~0.2 are recommended. Be aware that fluctuations on this scale in initial conditions may cause immediate refinement to the maximum level. Default: 1.0e-2
RefineByJeansLengthSafetyFactor (external)
If the Jeans length refinement criterion (see CellFlaggingMethod) is being used, then this parameter specifies the number of cells which must cover one Jeans length. Default: 4
JeansRefinementColdTemperature (external)
If the Jeans length refinement criterion (see CellFlaggingMethod) is being used, and this parameter is greater than zero, this temperature will be used in all cells when calculating the Jeans length. If it is less than or equal to zero, it will be used as a temperature floor when calculating the Jeans length. Default: -1.0
RefineByResistiveLengthSafetyFactor (external)
Resistive length is defined as the curl of the magnetic field over the magnitude of the magnetic field. We make sure this length is covered by this number of cells. i.w. The resistive length in a MHD simulation should not be smaller than CellWidth * RefineByResistiveLengthSafetyFactor. Default: 2.0
MustRefineParticlesCreateParticles (external)

This parameter will flag dark matter particles in cosmological initial conditions as MustRefineParticles. If CellFlaggingMethod 8 is set, AMR will be restricted to cells surrounding MustRefineParticles. There are several different modes for creating MustRefineParticles with this parameter described below. Further information on how to use dark matter MustRefineParticles in cosmological simulations can be found here (link). Default: 0

1. If the user specifies MustRefineParticlesLeftEdge and MustRefineParticlesRightEdge, dark matter particles within the specified region are flagged. Otherwise, the code looks for an ascii input file called MustRefineParticlesFlaggingList.in that contains a list of particle ids to be flagged. The ids in this list must be sorted in ascending order.
2. For use with ellipsoidal masking in MUSIC initial conditions. This setting uses traditional static grids for intermediate resolution levels MUSIC will generate RefinementMask files and the ParticleTypeName parameter should be set to the name of these files.
3. Same as setting 2, except refinement on intermediate levels is not constrained by static grids. Instead, refinement around dark matter particles is allowed down to the level of a particle’s generation level. Refinement beyond this level is allowed around particles within the MUSIC ellipsoidal masking region. Note, dark matter particles corresponding to a generation level N are guaranteed to be refined to at least level N, but may also exist on levels N > 1 if in the vicinity of an N > 1 dark matter particle or a tagged must-refine particle.
4. Similar to setting 3, except dark matter particles corresponding to a generation level N are refined only to level N and no further. If two dark matter particles from different levels occupy the same cell, that cell will be refined to the coarser level. Tagged must-refine particles near coarse dark matter particles will be similarly de-refined. Compared to option 3, this can be used to prevent unnecessary mesh refinement in regions where coarser particles enter into higher resolution regions, slowing down the simulation. Note, with this setting, coarse boundary particles entering into a high resolution region will eventually lead to total derefinement of the region of interest.
MustRefineParticlesRefineToLevel (external)
The maximum level on which MustRefineParticles are required to refine to. Currently sink particles and MBH particles are required to be sitting at this level at all times. Default: 0
MustRefineParticlesRefineToLevelAutoAdjust (external)
The parameter above might not be handy in cosmological simulations if you want your MustRefineParticles to be refined to a certain physical length, not to a level whose cell size keeps changing. This parameter (positive integer in pc) allows you to do just that. For example, if you set MustRefineParticlesRefineToLevelAutoAdjust = 128 (pc), then the code will automatically calculate MustRefineParticlesRefineToLevel using the boxsize and redshift information. Default: 0 (FALSE)
MustRefineParticlesMinimumMass (external)
This was an experimental parameter to set a minimum for MustRefineParticles. Default: 0.0
MustRefineParticlesRegionLeftEdge (external)
Bottom-left corner of a region in which dark matter particles are flagged as MustRefineParticles in nested cosmological simulations. To be used with MustRefineParticlesCreateParticles = 1. Default: 0.0 0.0 0.0
MustRefineParticlesRegionRightEdge (external)
Top-right corner of a region in which dark matter particles are flagged as MustRefineParticles in nested cosmological simulations. To be used with MustRefineParticlesCreateParticles = 1. Default: 0.0 0.0 0.0
MustRefineRegionMinRefinementLevel (external)
Minimum level to which the rectangular solid volume defined by MustRefineRegionLeftEdge and MustRefineRegionRightEdge will be refined to at all times. (No default setting)
MustRefineRegionLeftEdge (external)
Bottom-left corner of refinement region. Must be within the overall refinement region. If using a moving refinement region, this will correspond to the bottom-left corner in the MustRefineRegionFile at this output time. If these parameters are not set, then the code will likely try to refine the entire domain to the forced refinement level before only doing it within the MustRefineRegion, which can take a long time. Default: 0.0 0.0 0.0
MustRefineRegionRightEdge (external)
Top-right corner of refinement region. Must be within the overall refinement region. If using a moving refinement region, this will correspond to the top-right corner in the MustRefineRegionFile at this output time. If these parameters are not set, then the code will likely try to refine the entire domain to the forced refinement level before only doing it within the MustRefineRegion, which can take a long time. Default: 1.0 1.0 1.0
MustRefineRegionTimeType (external)
If set, this controls how the first column of a MustRefineRegionFile (see below) is interpreted, 0 for code time, 1 for redshift. Default: -1, which is equivalent to ‘off’.
MustRefineRegionFile (external)

The name of a text file containing the corners of the time-evolving refinement region. The lines in the file change the values of MustRefineRegionLeft/RightEdge during the course of the simulation, and the lines are ordered in the file from early times to late times. The first column of data is the time index (in code units or redshift, see the parameter above) for the next six columns, which are the values of MustRefineRegionLeft/RightEdge, followed by a column giving the level of refinement. For example, this might be two lines from the text file when time is indexed by redshift:

2.05 0.493102 0.488106 0.501109 0.495102 0.490106 0.503109 10
2.00 0.493039 0.487908 0.501189 0.495039 0.489908 0.503189 10


In this case, the MustRefineRegion is refined to 10 levels of refinement, starting at the z=2.05 value and moves via linear interpolation until the z=2.00 value. The code will crash if the simulation starts before the earliest time given or evolves until after the latest time in the file. There is a maximum of 8000 lines in the file and there is no comment header line. Default: None.

UseCoolingRefineRegion (external)
1 if using a CoolingRefineRegion; 0 if not. If this is set, then the CoolingRefineRegion is a rectilinear region in which refinement can be based on the cooling time (CellFlaggingMethod 7 must be set) but refinement based on the cooling time will not occur outside of this region. Default: 0
EvolveCoolingRefineRegion (external)
1 if the CoolingRefineRegion is evolving; 0 if not. Default: 0
CoolingRefineRegionLeftEdge (external)
Bottom-left corner of refinement region. Must be within the overall refinement region. If using a moving refinement region, this will correspond to the bottom-left corner in the CoolingRefineRegionFile at this output time. If these parameters are not set, then the code will likely try to refine the entire domain to the forced refinement level before only doing it within the CoolingRefineRegion, which can take a long time. Default: 0.0 0.0 0.0
CoolingRefineRegionRightEdge (external)
Top-right corner of refinement region. Must be within the overall refinement region. If using a moving refinement region, this will correspond to the top-right corner in the CoolingRefineRegionFile at this output time. If these parameters are not set, then the code will likely try to refine the entire domain to the forced refinement level before only doing it within the CoolingRefineRegion, which can take a long time. Default: 1.0 1.0 1.0
CoolingRefineRegionTimeType (external)
If set, this controls how the first column of a CoolingRefineRegionFile (see below) is interpreted, 0 for code time, 1 for redshift. Default: -1, which is equivalent to ‘off’.
CoolingRefineRegionFile (external)
The name of a text file containing the corners of the time-evolving cooling refinement region. The file format is the same as for a MustRefineRegionFile, but though the final column (refinement level) must be included, it is currently ignored by the code and the cooling refinement level is instead set to the MaximumRefinementLevel. Default: None.
StaticRefineRegionLevel[#] (external)
This parameter is used to specify regions of the problem that are to be statically refined, regardless of other parameters. This is mostly used as an internal mechanism to keep the initial grid hierarchy in place, but can be specified by the user. Up to 20 static regions may be defined (this number set in macros_and_parameters.h), and each static region is labeled starting from zero. For each static refined region, two pieces of information are required: (1) the region (see the next two parameters), and (2) the level at which the refinement is to occurs (0 implies a level 1 region will always exist). Default: none
StaticRefineRegionLeftEdge[#], StaticRefineRegionRightEdge[#] (external)
These two parameters specify the two corners of a statically refined region (see the previous parameter). Default: none
AvoidRefineRegionLevel[#] (external)
This parameter is used to limit the refinement to this level in a rectangular region. Up to MAX_STATIC_REGIONS regions can be used. Default: IND_UNDEFINED
AvoidRefineRegionLeftEdge[#], AvoidRefineRegionRightEdge[#] (external)
These two parameters specify the two corners of a region that limits refinement to a certain level (see the previous parameter). Default: none
MultiRefineRegionGeometry[#] (external)
This parameter (and the ones following) describe a physical region of the simulation box for which an independent refinement maximum and minimum (separate from MaximumRefinementLevel) can be specified.
MultiRefineRegionGeometry[#] controls the geometry of the refined volume. Currently implemented
geometries are: (0) a rectangular region, (1) a ring of infinite height and (2) a cylinder of infinite height. Up to 20 multi-refined regions may be defined (number the same as for StaticRefineRegion) and each multi-refined region is labelled starting from zero. Default: -1 (no multi-regions)
MultiRefineRegionLeftEdge[#], MultiRefineRegionRightEdge[#] (external)
Used when MultiRefineRegionGeometry[#] = 0 and specifies the two corners in code units of a rectangular multi-region with a given maximum and minimum refinement level. Default: none.
MultiRefineRegionCenter[#] (external)
Used when MultiRefineRegionGeometry[#] = 1 or 2 and specifies the center of the ring or cylinder in code units. Default: none
MultiRefineRegionRadius[#] (external)
Used when MultiRefineRegionGeometry[#] = 1 or 2 and specifies the radius of the ring or cylinder in code units. In the case of the ring, this marks the distance to the middle of the ring’s thickness. The thickness is specified with MultiRefineRegionWidth. Default: none
MultiRefineRegionWidth[#] (external)
Used when MultiRefineRegionGeometry[#] = 1 and specifies the width (thickness) of the ring in code units. Default: none
MultiRefineRegionOrientation[#] (external)
Used when MultiRefineRegionGeometry[#] = 1 or 2 and is a unit vector pointing along the vertical direction of the ring or cylinder. Default: none.
MultiRefineRegionStaggeredRefinement[#] (external)
Used when MultiRefineRegionGeometry[#] = 1 or 2. To avoid a sharp change in refinement at the edge of the ring or cylinder, the allowed refinement is staggered from the maximum allowed value outside the region, MultiRefineRegionOuterMaximumLevel, to the maximum allowed refinement inside the region, MultiRefineRegionMaximumLevel. This parameter is the length over which that staggering occurs in code units. Default: 0.0 (no staggering)
MultiRefineRegionMaximumLevel[#], MultiRefineRegionMinimumLevel[#] (external)
Maximum and minimum allowed refinement inside the region. Default: MaximumRefinementLevel, 0
MultiRefineRegionMaximumOuterLevel, MultiRefineRegionMinimumOuterLevel (external)
Maximum and minimum allowed refinement outside all regions. Default: MaximumRefinementLevel, 0
MinimumEfficiency (external)
When new grids are created during the rebuilding process, each grid is split up by a recursive bisection process that continues until a subgrid is either of a minimum size or has an efficiency higher than this value. The efficiency is the ratio of flagged zones (those requiring refinement) to the total number of zones in the grid. This is a number between 0 and 1 and should probably by around 0.4 for standard three-dimensional runs. Default: 0.2
NumberOfBufferZones (external)
Each flagged cell, during the regridding process, is surrounded by a number of zones to prevent the phenomenon of interest from leaving the refined region before the next regrid. This integer parameter controls the number required, which should almost always be one. Default: 1
MinimumSubgridEdge (external)
The minimum length of the edge of a subgrid. See Running Large Simulations. Default: 6
MaximumSubgridSize (external)
The maximum size (volume) of a subgrid. See Running Large Simulations. Default: 32768
CriticalGridRatio (external)
Critical grid ratio above which subgrids will be split in half along their long axis prior to being split by the second derivative of their signature. Default: 3.0
SubgridSizeAutoAdjust (external)
See Running Large Simulations. Default: 1 (TRUE)
OptimalSubgridsPerProcessor (external)
See Running Large Simulations. Default: 16
LoadBalancing (external)
Set to 0 to keep child grids on the same processor as their parents. Set to 1 to balance the work on one level over all processors. Set to 2 or 3 to load balance the grids but keep them on the same node. Option 2 assumes grouped scheduling, i.e. proc # = (01234567) reside on node (00112233) if there are 4 nodes. Option 3 assumes round-robin scheduling (proc = (01234567) -> node = (01230123)). Set to 4 for load balancing along a Hilbert space-filling curve on each level. See Running Large Simulations. Default: 1
LoadBalancingCycleSkip (external)
This sets how many cycles pass before we load balance the root grids. Only works with LoadBalancing set to 2 or 3. NOT RECOMMENDED for nested grid calculations. Default: 10
LoadBalancingMinLevel (external)
Load balance the grids in levels greater than this parameter. Default: 0
LoadBalancingMaxLevel (external)
Load balance the grids in levels less than this parameter. Default: MAX_DEPTH_OF_HIERARCHY
ResetLoadBalancing (external)
When restarting a simulation, this parameter resets the processor number of each root grid to be sequential. All child grids are assigned to the processor of their parent grid. Only implemented for LoadBalancing = 1. Default = 0
NumberOfRootGridTilesPerDimensionPerProcessor (external)
Splits the root grid into 2^(dimensions*this parameter) grids per MPI process. Default: 1
UserDefinedRootGridLayout (external)

A three element array. Splits the root grid into N subgrids where N is the product of the supplied values. The first entry corresponds to the number of root grid decompositions along the x axis of the simulation, the second element the number of decompositions along the y axis, and the third the number of decompositions along the z axis.

This parameter is only used if all three elements of the array are set to a value different from the dummy default value. If that is the case the root grid will be manually decomposed and the value supplied for NumberOfRootGridTilesPerDimensionPerProcessor will be ignored. This is most useful when an automatic root grid decomposition is inefficient (for example, in a deeply nested isolated galaxy simulation).

This parameter should be used with caution since it is possible to get into a situation where there are fewer grids than CPU cores. Normally this can never happen since there will always be at least one root grid tile for every CPU. Most simulations assume you will be running with as many root grid tiles as CPUs - if you instead opt to reduce the number of root grid tiles per CPU to a number less than one, Enzo might break in unpredictable ways. Default: -99999 -99999 -99999

FastSiblingLocatorEntireDomain (external)
In zoom-in calculations, the fast sibling locator doesn’t need to search the entire domain. Turning this parameter on restricts the finder to the inner nested grid. Currently broken. Default: 0
MoveParticlesBetweenSiblings (external)
During RebuildHierarchy, particles that have moved beyond the grid boundaries are moved to the correct grid. Default: 1
RebuildHierarchyCycleSkip (external)
Set the number of cycles at a given level before rebuilding the hierarchy. Example: RebuildHierarchyCycleSkip[1] = 4

## Gravity Parameters¶

### General Gravity Parameters¶

TopGridGravityBoundary (external)
A single integer which specified the type of gravitational boundary conditions for the top grid. Possible values are 0 for periodic and 1 for isolated (for all dimensions). The isolated boundary conditions have not been tested recently, so caveat emptor. Default: 0
SelfGravity (external)
This flag (1 - on, 0 - off) indicates if the baryons and particles undergo self-gravity.
SelfGravityGasOff (external)
This parameter is used in conjunction with SelfGravity so that only particles contribute to potential, not gas. Default = False (i.e. gas does contribute)
GravitationalConstant (external)
This is the gravitational constant to be used in code units. For cgs units it should be 4*pi*G. For cosmology, this value must be 1 for the standard units to hold. A more detailed description can be found at Enzo Internal Unit System. Default: 4*pi.
PotentialIterations (external)
Number of iterations to solve the potential on the subgrids. Values less than 4 sometimes will result in slight overdensities on grid boundaries. Default: 4.
MaximumGravityRefinementLevel (external)
This is the lowest (most refined) depth that a gravitational acceleration field is computed. More refined levels interpolate from this level, providing a mechanism for instituting a minimum gravitational smoothing length. Default: MaximumRefinementLevel
MaximumParticleRefinementLevel (external)
This is the level at which the dark matter particle contribution to the gravity is smoothed. This works in an inefficient way (it actually smoothes the particle density onto the grid), and so is only intended for highly refined regions which are nearly completely baryon dominated. It is used to remove the discreteness effects of the few remaining dark matter particles. Not used if set to a value less than 0. Default: -1
ParticleSubgridDepositMode (external)

This parameter controls how particles stored in subgrid are deposited into the current grid. Options are:

1. (CIC_DEPOSIT) - This is a second-order, cloud-in-cell deposition
method in which the cloud size is equal to the cell size in the target grid (particles are in source grid, deposited into target grid). This method preserves the correct center-of-mass for a single particle but smears out boundaries and can result in small artifacts for smooth particle distributions (e.g. nested cosmological simulations with low perturbations).
2. (CIC_DEPOSIT_SMALL) - This is also a CIC method, but the cloud
size is taken to be the cell size in the source grid, so for subgrids, the cloud is smaller than the grid size. This is an attempt to compromise between the other two methods.
3. (NGP_DEPOSIT) - This uses a first order, nearest-grid-point method to deposit particle mass. It does not preserve center- of mass position and so for single particle results in noisy accelerations. However, it does correctly treat nested cosmology simulations with low initial perturbations.

Default: 1

BaryonSelfGravityApproximation (external)
This flag indicates if baryon density is derived in a strange, expensive but self-consistent way (0 - off), or by a completely reasonable and much faster approximation (1 - on). This is an experiment gone wrong; leave on. Well, actually, it’s important for very dense structures as when radiative cooling is turned on, so set to 0 if using many levels and radiative cooling is on [ignored in current version]. Default: 1

### External Gravity Source¶

These parameters set up an external static background gravity source that is added to the acceleration field for the baryons and particles.

PointSourceGravity (external)
This parameter indicates that there is to be a (constant) gravitational field with a point source profile (PointSourceGravity = 1) or NFW profile (PointSourceGravity = 2). Default: 0
PointSourceGravityConstant (external)
If PointSourceGravity = 1, this is the magnitude of the point source acceleration at a distance of 1 length unit (i.e. GM in code units). If PointSourceGravity = 2, then it takes the mass of the dark matter halo in CGS units. ProblemType = 31 (galaxy disk simulation) automatically calculates values for PointSourceGravityConstant and PointSourceGravityCoreRadius. ProblemType = 108 (elliptical galaxy and galaxy cluster) also includes the gravity from the stellar component and the SMBH. Default: 1
PointSourceGravityCoreRadius (external)
For PointSourceGravity = 1, this is the radius inside which the acceleration field is smoothed in code units. With PointSourceGravity = 2, it is the scale radius, rs, in CGS units (see Navarro, Frank & White, 1997). Default: 0
PointSourceGravityPosition (external)
If the PointSourceGravity flag is turned on, this parameter specifies the center of the point-source gravitational field in code units. Default: 0 0 0
ExternalGravity (external)
This fulfills the same purpose as PointSourceGravity but is more aptly named. ExternalGravity = 1 turns on an alternative implementation of the NFW profile with properties defined via the parameters HaloCentralDensity, HaloConcentration and HaloVirialRadius. Boxsize is assumed to be 1.0 in this case. ExternalGravity = 10 gives a gravitational field defined by the logarithmic potential in Binney & Tremaine, corresponding to a disk with constant circular velocity. Default: 0
ExternalGravityConstant (external)
If ExternalGravity = 10, this is the circular velocity of the disk in code units. Default: 0.0
ExternalGravityDensity
Reserved for future use.
ExternalGravityPosition (external)
If ExternalGravity = 10, this parameter specifies the center of the gravitational field in code units. Default: 0 0 0
ExternalGravityOrientation (external)
For ExternalGravity = 10, this is the unit vector of the disk’s angular momentum (e.g. a disk whose face-on view is oriented in the x-y plane would have ExternalGravityOrientation = 0 0 1). Default: 0 0 0
ExternalGravityRadius (external)
If ExternalGravity = 10, this marks the inner radius of the disk in code units within which the velocity drops to zero. Default: 0.0
UniformGravity (external)
This flag (1 - on, 0 - off) indicates if there is to be a uniform gravitational field. Default: 0
UniformGravityDirection (external)
This integer is the direction of the uniform gravitational field: 0 - along the x axis, 1 - y axis, 2 - z axis. Default: 0
UniformGravityConstant (external)
Magnitude (and sign) of the uniform gravitational acceleration. Default: 1
DiskGravity (external)
This flag (1 - on, 0 - off) indicates if there is to be a disk-like gravity field (Berkert 1995; Mori & Burkert 2000). Default: 0
DiskGravityPosition (external)
This indicates the position of the center of the disk gravity. Default: 0 0 0
DiskGravityAngularMomentum (external)
Specifies the unit vector of the disk angular momentum. Default: 0 0 1
DiskGravityStellarDiskMass (external)
Total mass of stellar disk (in solar masses) Default: 1e11
DiskGravityDiskScaleHeightR (external)
Disk scale length in radius (in Mpc) Default: 4.0e-3
DiskGravityDiskScaleHeightz (external)
Disk scale height in z (in Mpc) Default: 2.5e-4
DiskGravityStellarBulgeMass (external)
Disk stellar bulge mass (in solar masses) Default: 1.0e10
DiskGravityStellarBulgeR (external)
Disk stellar bulge scalue radius (in Mpc) Default: 1.0e-4
DiskGravityDarkMatterR (external)
Dark matter halo scale radius (in Mpc) Default: 2.3e-2
DiskGravityDarkMatterDensity (external)
Dark matter effective density (in cgs) Default: 3.81323e-25

## Hydrodynamics Parameters¶

### General Hydrodynamics Parameters¶

UseHydro (external)
This flag (1 - on, 0 - off) controls whether a hydro solver is used. Default: 1
HydroMethod (external)

This integer specifies the hydrodynamics method that will be used. Currently implemented are

Hydro method Description
0 PPM DE (a direct-Eulerian version of PPM)
1 [reserved]
2 ZEUS (a Cartesian, 3D version of Stone & Norman). Note that if ZEUS is selected, it automatically turns off ConservativeInterpolation and the DualEnergyFormalism flags.
3 Runge Kutta second-order based MUSCL solvers.
4 Same as 3 but including Dedner MHD (Wang & Abel 2008). For 3 and 4 there are the additional parameters RiemannSolver and ReconstructionMethod you want to set.
5 No Hydro (Testing only)
6 MHD with Constrained Transport.

Default: 0

More details on each of the above methods can be found at Hydro and MHD Methods.

FluxCorrection (external)
This flag indicates if the flux fix-up step should be carried out around the boundaries of the sub-grid to preserve conservation (0 - off, 1 - on, 2 - direct correction for color fields). Strictly speaking this should always be used, but we have found it to lead to a less accurate solution for cosmological simulations because of the relatively sharp density gradients involved. However, it does appear to be important when radiative cooling is turned on and very dense structures are created. It does work with the ZEUS hydro method, but since velocity is face-centered, momentum flux is not corrected. If FluxCorrection = 1, species quantities are not flux corrected directly but are modified to keep the fraction constant based on the density change. If FluxCorrection = 2, species quantities are flux corrected directly in the same way as density and energy. Default: 1
InterpolationMethod (external)

There should be a whole section devoted to the interpolation method, which is used to generate new sub-grids and to fill in the boundary zones of old sub-grids, but a brief summary must suffice. The possible values of this integer flag are shown in the table below. The names specify (in at least a rough sense) the order of the leading error term for a spatial Taylor expansion, as well as a letter for possible variants within that order. The basic problem is that you would like your interpolation method to be: multi-dimensional, accurate, monotonic and conservative. There doesn’t appear to be much literature on this, so I’ve had to experiment. The first one (ThirdOrderA) is time-consuming and probably not all that accurate. The second one (SecondOrderA) is the workhorse: it’s only problem is that it is not always symmetric. The next one (SecondOrderB) is a failed experiment, and SecondOrderC is not conservative. FirstOrderA is everything except for accurate. If HydroMethod = 2 (ZEUS), this flag is ignored, and the code automatically uses SecondOrderC for velocities and FirstOrderA for cell-centered quantities. Default: 1

0 - ThirdOrderA     3 - SecondOrderC
1 - SecondOrderA    4 - FirstOrderA
2 - SecondOrderB

ConservativeInterpolation (external)
This flag (1 - on, 0 - off) indicates if the interpolation should be done in the conserved quantities (e.g. momentum rather than velocity). Ideally, this should be done, but it can cause problems when strong density gradients occur. This must(!) be set off for ZEUS hydro (the code does it automatically). Default: 1
RiemannSolver (external)

This integer specifies the Riemann solver. Solver options, and the relevant hydro method, are summarized as follows:

Riemann solver HydroMethod Description
0 [reserved]
1 0,3,4 HLL (Harten-Lax-van Leer) a two-wave, three-state solver with no resolution of contact waves
2   [reserved]
3 3,4 LLF (Local Lax-Friedrichs)
4 0,3 HLLC (Harten-Lax-van Leer with Contact) a three-wave, four-state solver with better resolution of contacts
5 0 TwoShock
6 4,6 HLLD

Default: 1 (HLL) for HydroMethod = 3; 5 (TwoShock) for HydroMethod = 0; 6 (HLLD) for HydroMethod = 6

RiemannSolverFallback (external; only if HydroMethod is 0, 3 or 4)
If the euler update results in a negative density or energy, the solver will fallback to the HLL Riemann solver that is more diffusive only for the failing cell. Only active when using the HLLC or TwoShock Riemann solver. Default: OFF.
ReconstructionMethod (external; only if HydroMethod is 3 or 4)

This integer specifies the reconstruction method for the MUSCL solver. Choice of

Reconstruction Method HydroMethod Description
0 0,3,4,6 PLM (piecewise linear)
1 0 PPM (piecwise parabolic)
2   [reserved]
3   [reserved]
4   [reserved]
6 6 MUSCL-Hancock (Non Runge-Kutta)

Default: 0 (PLM) for HydroMethod = 3; 1 (PPM) for HydroMethod = 0

ConservativeReconstruction (external; only if HydroMethod is 3 or 4)
Experimental. This option turns on the reconstruction of the left/right interfaces in the Riemann problem in the conserved variables (density, momentum, and energy) instead of the primitive variables (density, velocity, and pressure). This generally gives better results in constant-mesh problems has been problematic in AMR simulations. Default: OFF
PositiveReconstruction (external; only if HydroMethod is 3 or 4)
Experimental and not working. This forces the Riemann solver to restrict the fluxes to always give positive pressure. Attempts to use the Waagan (2009), JCP, 228, 8609 method. Default: OFF
Gamma (external)
The ratio of specific heats for an ideal gas (used by all hydro methods). If using multiple species (i.e. MultiSpecies > 0), then this value is ignored in favor of a direct calculation (except for PPM LR) Default: 5/3.
Mu (external)
The molecular weight. Default: 0.6.
CourantSafetyNumber (external)
This is the maximum fraction of the CFL-implied timestep that will be used to advance any grid. A value greater than 1 is unstable (for all explicit methods). The recommended value is 0.4. Default: 0.6.
RootGridCourantSafetyNumber (external)
This is the maximum fraction of the CFL-implied timestep that will be used to advance ONLY the root grid. When using simulations with star particle creation turned on, this should be set to a value of approximately 0.01-0.02 to keep star particles from flying all over the place. Otherwise, this does not need to be set, and in any case should never be set to a value greater than 1.0. Default: 1.0.
UseCoolingTimestep (external)
This parameter will limit the timestep on each level by some fraction of the minimum cooling time on the level, where this fraction is set by CoolingTimestepSafetyFactor. In most cases, this will substantially decrease the timesteps, depending on the local cooling time, and thus increase the run time of any simulation. Default: OFF
CoolingTimestepSafetyFactor (external)
Described in UseCoolingTime. Default: 0.1
DualEnergyFormalism (external)
The dual energy formalism is needed to make total energy schemes such as PPM DE and PPM LR stable and accurate in the “hyper-Machian” regime (i.e. where the ratio of thermal energy to total energy < ~0.001). Turn on for cosmology runs with PPM DE and PPM LR. Automatically turned off when used with the hydro method ZEUS. Integer flag (0 - off, 1 - on). When turned on, there are two energy fields: total energy and thermal energy. Default: 0
DualEnergyFormalismEta1, DualEnergyFormalismEta2 (external)
These two parameters are part of the dual energy formalism and should probably not be changed. Defaults: 0.001 and 0.1 respectively.
PressureFree (external)
A flag that is interpreted by the PPM DE hydro method as an indicator that it should try and mimic a pressure-free fluid. A flag: 1 is on, 0 is off. Default: 0
PPMFlatteningParameter (external)
This is a PPM parameter to control noise for slowly-moving shocks. It is either on (1) or off (0). Default: 0
PPMDiffusionParameter (external)
This is the PPM diffusion parameter (see the Colella and Woodward method paper for more details). It is either on (1) or off (0). Default: 1 [Currently disabled (set to 0)]
PPMSteepeningParameter (external)
A PPM modification designed to sharpen contact discontinuities. It is either on (1) or off (0). Default: 0
SmallRho (external)
Minimum value for density in code units. This is enforced in euler.F when using the PPM solver (HydroMethod = 0) or in hydro_rk/EvolveLevel_RK.C when HydroMethod is 3 or 4. Not enforced in other hydrodynamics methods. Default: 1e-30
ZEUSQuadraticArtificialViscosity (external)
This is the quadratic artificial viscosity parameter C2 of Stone & Norman, and corresponds (roughly) to the number of zones over which a shock is spread. Default: 2.0
ZEUSLinearArtificialViscosity (external)
This is the linear artificial viscosity parameter C1 of Stone & Norman. Default: 0.0

### Minimum Pressure Support Parameters¶

UseMinimumPressureSupport (external)
When radiative cooling is turned on, and objects are allowed to collapse to very small sizes so that their Jeans length is no longer resolved, then they may undergo artificial fragmentation and angular momentum non-conservation. To alleviate this problem, as discussed in more detail in Machacek, Bryan & Abel (2001), a very simple fudge was introduced: if this flag is turned on, then a minimum temperature is applied to grids with level == MaximumRefinementLevel. This minimum temperature is that required to make each cell Jeans stable multiplied by the parameter below. More precisely, the temperature of a cell is set such that the resulting Jeans length is the square-root of the parameter MinimumPressureSupportParameter. So, for the default value of 100 (see below), this insures that the ratio of the Jeans length/cell size is at least 10. Default: 0
MinimumPressureSupportParameter (external)
This is the numerical parameter discussed above. Default: 100

### Magnetohydrodynamics (CT) Parameters¶

MHD_CT_Method (external)

Method for computing the electric field from the Riemann fluxes

CT Method Description
0 None (only for debugging)
1 Balsara and Spicer 1999. First order average.
2 Gardiner and Stone 2005. Second order Lax-Friedrichs type reconstruction. Uses CT_AthenaDissipation flag.
3 Gardiner and Stone 2005. Second order reconstruction using upwind switches

Default: 3

CT_AthenaDissipation (external)
For the Lax-Friedrichs CT method, this is the maximum wave speed. ( in Gardiner & Stone 2005 eqn. 46). Default: 0.1
EquationOfState (external, ct only)
0: standard adiabatic 1: Exactly isothermal equation of state. This flag removes the total energy term completely, instead computing pressure as . This option only works with HydroMethod = 6 and RiemannSolver = 6 (HLLD) as this is the only purely isothermal Riemann solver in Enzo. Default: 0
IsothermalSoundSpeed (external, ct only)
When EquationOfState = 1, this is the sound speed used for computation of pressure. Default: 1
MHDCTSlopeLimiter (external, ct only)
For computing derivatives for the reconstruction, this switches between zero slope (0), minmod (1), VanLeer (2), and characteristic (3) characteristic with primitive limiting (4). Default: 1
ReconstructionMethod (external)
There are two reconstruction methods that work with MHDCT: Piecewise Linear Method (PLM) (0) and MUSCL-Hancock (6). This formulation of MUSCL-Hancock is different from the 2nd order Runga Kutta used for HydroMethod = 3,4.
RiemannSolver (external)
As with HydroMethod=4, the preferred solver is HLLD (RiemannSolver=6). Other solvers may be released if the DOE approves them.
MHDCTUseSpecificEnergy (external)
Either specific energy is used internally (1) or conserved energy is used internally (0). Minor difference in boundary condition update, included for comparison to old solutions. Default: 1
MHDCTDualEnergyMethod (external)
When DualEnergyFormalism = 1, this switches between a method that solves an additional equation for the internal energy, as in the rest of Enzo, and method that updates the entropy.
MHD_WriteElectric (external)
Include the electric field in the output. Default: 0
MHD_ProjectB (internal)
Project magnetic fields from fine to coarse. Should not be done in general, only used for initialization.
MHD_ProjectE (internal)
Project Electric fields from fine to coarse. Used for the time evolution of the fields.

### Magnetohydrodynamics (Dedner) Parameters¶

The following parameters are considered only when HydroMethod is 3 or 4 (and occasionally only in some test problems). Because many of the following parameters are not actively being tested and maintained, users are encouraged to carefully examine the code before using it.

UsePoissonDivergenceCleaning (external)
Enables additional divergence cleaning by solving a Poisson equation. This works on top of the standard mixed hyperbolic/parabolic divergence cleaning and is not necessary for the proper operation of the solver. This works on individual grids, i.e., it’s not a global divergence purge. Use with care as this feature is not extensively tested. No recommendation about the use of this option is made by the developers at this time. Method 1 and 2 are a failed experiment to do divergence cleaning using successive over relaxation. Method 3 uses conjugate gradient with a 2 cell stencil and Method 4 uses a 4 cell stencil. 4 is more accurate but can lead to aliasing effects. Default: 0
PoissonDivergenceCleaningBoundaryBuffer (external)
Choose to not correct in the active zone of a grid by a boundary of cells this thick. Default: 0
PoissonDivergenceCleaningThreshold (external)
Calls divergence cleaning on a grid when magnetic field divergence is above this threshold. Default: 0.001
PoissonApproximationThreshold (external)
Controls the accuracy of the resulting solution for divergence cleaning Poisson solver. Default: 0.001
PoissonBoundaryType (external)
Controls the boundary conditions for divergence cleaning Poisson solver. 0 - Neumann (default). 1 - Dirichlet
UseDrivingField (external)
This parameter is used to add external driving force as a source term in some test problems; see hydro_rk/Grid_(MHD)SourceTerms.C. Default: 0
DrivingEfficiency (external)
This parameter is used to define the efficiency of such driving force; see hydro_rk/Grid_(MHD)SourceTerms.C. Default: 1.0
UseConstantAcceleration (external)
This parameter is used to add constant acceleration as a source term in some set-ups; see hydro_rk/Grid_(MHD)SourceTerms.C. Default: 0
ConstantAcceleration[] (external)
This parameter is used to define the value of such acceleration; see hydro_rk/Grid_(MHD)SourceTerms.C.
UseViscosity (external)
This parameter is used to add viscosity and thereby update velocity in some set-ups (1 - constant viscosity, 2 - alpha viscosity); see ComputeViscosity in hydro_rk/Grid_AddViscosity.C. Default: 0
ViscosityCoefficient (external)
This parameter is used to define the value of such viscosity for UseViscosity = 1; see ComputeViscosity in hydro_rk/Grid_AddViscosity.C. Default: 0.0
UseGasDrag (external)
This parameter is used to calculate velocity decrease caused by gas drag as a source term in some set-ups; see hydro_rk/Grid_(MHD)SourceTerms.C. Default: 0
GasDragCoefficient (external)
This parameter is used to define the value of such gas drag; see hydro_rk/Grid_(MHD)SourceTerms.C. Default: 0.0
UseFloor (external)
This parameter is used to impose the minimum energy based on MaximumAlvenSpeed in some set-ups; see hydro_rk/Grid_SetFloor.C. Default: 0
MaximumAlvenSpeed (external)
This parameter is used to define the value of such minimum; see hydro_rk/Grid_SetFloor.C. Default: 1e30
UseAmbipolarDiffusion (external)
This parameter is used to update magnetic fields by ambipolar diffusion in some set-ups; see hydro_rk/Grid_AddAmbipolarDiffusion.C. Default: 0
UseResistivity (external)
This parameter is used to add resistivity and thereby update magnetic fields in some set-ups; see ComputeResistivity in hydro_rk/Grid_AddResistivity.C. Default: 0
UsePhysicalUnit (external)
For some test problems (mostly in hydro_rk), the relevant parameters could be defined in physical CGS units. Default: 0
MixSpeciesAndColors (external)
This parameter enables color fields to be evolved as species in the MUSCL solvers. If PopIIISupernovaUseColour is on, this must also be turned on to trace the metal field. Default: 1
SmallT (external)
Minimum value for temperature in hydro_rk/EvolveLevel_RK.C. Default: 1e-10 (note that the default value assumes UsePhysicalUnit = 1)
SmallP
[not used]
Theta_Limiter (external)
Flux limiter in the minmod Van Leer formulation. Must be between 1 (most dissipative) and 2 (least dissipative). Default: 1.5
Coordinate (external)
Coordinate systems to be used in hydro_rk/EvolveLevel_RK.C. Currently implemented are Cartesian and Spherical for HD_RK, and Cartesian and Cylindrical for MHD_RK. See Grid_(MHD)SourceTerms.C. Default: Cartesian
EOSType (external)
Types of Equation of State used in hydro_rk/EvolveLevel_RK.C (0 - ideal gas, 1 - polytropic EOS, 2 - another polytropic EOS, 3 - isothermal, 4 - pseudo cooling, 5 - another pseudo cooling, 6 - minimum pressure, 7 - Fedderath et al. 2010); see hydro_rk/EOS.h. Default: 0
EOSSoundSpeed (external)
Sound speed to be used in EOS.h for EOSType = 1, 2, 3, 4, 5. Default: 2.65e4
EOSCriticalDensity (external)
Critical density to be used in EOS.h for EOSType = 1, 2, 4, 6. Default: 1e-13
EOSGamma (external)
Polytropic gamma to be used in EOS.h for EOSType = 1. Default: 1.667
DivBDampingLength (external)
From C_h (the Dedner wave speeds at which the div*B error is isotropically transferred; as defined in e.g. Matsumoto, PASJ, 2007, 59, 905) and this parameter, C_p (the decay rate of the wave) is calculated; see ComputeDednerWaveSpeeds.C Default: 1.0
UseCUDA (external)
Set to 1 to use the CUDA-accelerated (M)HD solver. Only works if compiled with cuda-yes. Default: 0
ResetMagneticField (external)
Set to 1 to reset the magnetic field in the regions that are denser than the critical matter density. Very handy when you want to re-simulate or restart the dumps with MHD. Default: 0
ResetMagneticFieldAmplitude (external)
The magnetic field values (in Gauss) that will be used for the above parameter. Default: 0.0 0.0 0.0

## Cooling Parameters¶

### Simple Cooling Options¶

RadiativeCooling (external)

This flag (1 - on, 0 - off) controls whether or not a radiative cooling module is called for each grid. There are currently several possibilities, controlled by the value of another flag. See Gas Chemistry, Cooling, and Heating for more information on the various cooling methods. Default: 0

• If the MultiSpecies flag is off, then equilibrium cooling is assumed and one of the following two will happen. If the parameter GadgetCooling is set to 1, the primordial equilibrium code is called (see below). If GadgetCooling is set to 0, a file called cool_rates.in is read to set a cooling curve. This file consists of a set of temperature and the associated cgs cooling rate; a sample compute with a metallicity Z=0.3 Raymond-Smith code is provided in input/cool_rates.in. This has a cutoff at 10000 K (Sarazin & White 1987). Another choice will be input/cool_rates.in_300K which goes further down to 300 K (Rosen & Bregman 1995).
• If the MultiSpecies flag is on, then the cooling rate is computed directly by the species abundances. This routine (which uses a backward differenced multi-step algorithm) is borrowed from the Hercules code written by Peter Anninos and Yu Zhang, featuring rates from Tom Abel. Other varieties of cooling are controlled by the MetalCooling parameter, as discused below.
RadiativeCoolingModel (external)
This switches between the tabular look up cooling that is standard (RadiativeCoolingModel=1) and an analytic fit to the Wolfire et al 2003, ApJ, 587, 278 made by Koyama and Inutsuka 2006 (RadiativeCoolingModel = 3, arXiv:astro-ph/0605528). Default: 1
GadgetCooling (external)
This flag (1 - on, 0 - off) turns on (when set to 1) a set of routines that calculate cooling rates based on the assumption of a six-species primordial gas (H, He, no H2 or D) in equilibrium, and is valid for temperatures greater than 10,000 K. This requires the file TREECOOL to execute. Default: 0
GadgetEquilibriumCooling (external)
An implementation of the ionization equilibrium cooling code used in the GADGET code which includes both radiative cooling and a uniform metagalactic UV background specified by the TREECOOL file (in the amr_mpi/exe directory). When this parameter is turned on, MultiSpecies and RadiationFieldType are forced to 0 and RadiativeCooling is forced to 1. [Not in public release version]
MetalCooling (external)
This flag (0 - off, 1 - metal cooling from Glover & Jappsen 2007, 2 - Cen et al (1995), 3 - Cloudy cooling from Smith, Sigurdsson, & Abel 2008) turns on metal cooling for runs that track metallicity. Option 1 is valid for temperatures between 100 K and 108K because it considers fine-structure line emission from carbon, oxygen, and silicon and includes the additional metal cooling rates from Sutherland & Dopita (1993). Option 2 is only valid for temperatures above 104K. Option 3 uses multi-dimensional tables of heating/cooling values created with Cloudy and optionally coupled to the MultiSpecies chemistry/cooling solver. This method is valid from 10 K to 108K. See the Cloudy Cooling parameters below. Default: 0.
MetalCoolingTable (internal)
This field contains the metal cooling table required for MetalCooling option 1. In the top level directory input/, there are two files metal_cool.dat and metal_cool_pop3.dat that consider metal cooling for solar abundance and abundances from pair-instability supernovae, respectively. In the same directory, one can find an IDL routine (make_Zcool_table.pro) that generates these tables. Default: metal_cool.dat
MultiSpecies (external)
If this flag (1, 2, 3- on, 0 - off) is on, then the code follows not just the total density, but also the ionization states of Hydrogen and Helium. If set to 2, then a nine-species model (including H2, H2+ and H-) will be computed, otherwise only six species are followed (H, H+, He, He+, He++, e-). If set to 3, then a 12 species model is followed, including D, D+ and HD. This routine, like the last one, is based on work done by Abel, Zhang and Anninos. Default: 0
MultiMetals (external)
This was added so that the user could turn on or off additional metal fields - currently there is the standard metallicity field (Metal_Density) and two additional metal fields (Z_Field1 and Z_Field2). Acceptable values are 1 or 0, Default: 0 (off).
ThreeBodyRate (external)
Which Three Body rate should be used for H2 formation?: 0 = Abel, Bryan, Norman 2002, 1 = PSS83, 2= CW83, 3 = FH07, 4= G08. (See Turk et al 2011 <http://adsabs.harvard.edu/abs/2011ApJ…726…55T>)
CIECooling (external)
Should CIE (Ripamonti & Abel 2004 <http://adsabs.harvard.edu/abs/2004MNRAS.348.1019R>) cooling be included at high densities?
H2OpticalDepthApproximation (external)
Should the H2 cooling be attenuated? Taken from Ripamonti & Abel 2004 <http://adsabs.harvard.edu/abs/2004MNRAS.348.1019R>. Default: 1?
H2FormationOnDust (external)
Turns on H2 formation on dust grains and gas-grain heat transfer following Omukai (2000) <http://adsabs.harvard.edu/abs/2000ApJ…534..809O>. Default: 0 (OFF)
NumberOfDustTemperatureBins (external)
Number of dust temperature bins for the dust cooling and H2 formation rates. Default: 250
DustTemperatureStart (external)
Minimum dust temperature for dust rates. Default: 1.0
DustTemperatureEnd (external)
Maximum dust temperature for dust rates. Default: 1500
OutputDustTemperature (external)
Flag to write out the dust temperature field. Default: 0
PhotoelectricHeating (external)
If set to be 1, the following parameter will be added uniformly to the gas without any shielding (Tasker & Bryan 2008 <http://adsabs.harvard.edu/abs/2008ApJ…673..810T>). Default: 0
PhotoelectricHeatingRate (external)
This is the parameter used as Gamma_pe for uniform photoelectric heating. Default: 8.5e-26 erg s^-1 cm^-3

### Cloudy Cooling¶

Cloudy cooling from Smith, Sigurdsson, & Abel (2008) interpolates over tables of precomputed cooling data. Cloudy cooling is turned on by setting MetalCooling to 3. RadiativeCooling must also be set to 1. Depending on the cooling data used, it can be coupled with MultiSpecies = 1, 2, or 3 so that the metal-free cooling comes from the MultiSpecies machinery and the Cloudy tables provide only the metal cooling. Datasets range in dimension from 1 to 5. Dim 1: interpolate over temperature. Dim 2: density and temperature. Dim 3: density, metallicity, and temperature. Dim 4: density, metallicity, electron fraction, and temperature. Dim 5: density, metallicity, electron fraction, spectral strength, and temperature. See Smith, Sigurdsson, & Abel (2008) for more information on creating Cloudy datasets.

CloudyCoolingGridFile (external)
A string specifying the path to the Cloudy cooling dataset.
IncludeCloudyHeating (external)
An integer (0 or 1) specifying whether the heating rates are to be included in the calculation of the cooling. Some Cloudy datasets are made with the intention that only the cooling rates are to be used. Default: 0 (off).
CMBTemperatureFloor (external)
An integer (0 or 1) specifying whether a temperature floor is created at the temperature of the cosmic microwave background (TCMB = 2.72 (1 + z) K). This is accomplished in the code by subtracting the cooling rate at TCMB such that Cooling = Cooling(T) - Cooling(TCMB). Default: 1 (on).
CloudyElectronFractionFactor (external)
A float value to account for additional electrons contributed by metals. This is only used with Cloudy datasets with dimension greater than or equal to 4. The value of this factor is calculated as the sum of (Ai * i) over all elements i heavier than He, where Ai is the solar number abundance relative to H. For the solar abundance pattern from the latest version of Cloudy, using all metals through Zn, this value is 9.153959e-3. Default: 9.153959e-3.

### The Grackle¶

The Grackle is an external chemistry and cooling library originally derived from Enzo’s MultiSpecies chemistry and Cloudy cooling modules. See here for a full description, including why you might use this over Enzo’s internal chemistry and cooling. For more information on Grackle parameter, see also the Grackle documentation. Note, some Grackle parameters have been mapped to Enzo parameters for simplicity.

use_grackle (int)
Flag to use the Grackle machinery (1 - on, 0 - off). Default: 0.
with_radiative_cooling (int)
Flag to include radiative cooling and actually update the thermal energy during the chemistry solver. If off, the chemistry species will still be updated. The most common reason to set this to off is to iterate the chemistry network to an equilibrium state (1 - on, 0 - off). Default: 1.
MultiSpecies (int) [mapped to Grackle parameter primordial_chemistry]

Flag to control which primordial chemistry network is used. Default: 0.

• 0: no chemistry network. Radiative cooling for primordial species is solved by interpolating from lookup tables calculated with Cloudy.
• 1: 6-species atomic H and He. Active species: H, H+, He, He+, He++, e-.
• 2: 9-species network including atomic species above and species for molecular hydrogen formation. This network includes formation from the H- and H2+ channels, three-body formation (H+H+H and H+H+H2), H2 rotational transitions, chemical heating, and collision-induced emission (optional). Active species: above + H-, H2, H2+.
• 3: 12-species network include all above plus HD rotation cooling. Active species: above plus D, D+, HD.
H2FormationOnDust (int) [mapped to Grackle parameter h2_on_dust]
See Enzo equivalent above. Default: 0.
MetalCooling (int) [mapped to Grackle parameter metal_cooling]
Flag to enable metal cooling using the Cloudy tables. If enabled, the cooling table to be used must be specified with the grackle_data_file parameter (1 - on, 0 - off). Default: 0.
CMBTemperatureFloor (int) [mapped to Grackle parameter cmb_temperature_floor]
See Enzo equivalent above. Default: 1.
UVbackground (int)
Flag to enable a UV background. If enabled, the cooling table to be used must be specified with the grackle_data_file parameter (1 - on, 0 - off). Default: 0.
grackle_data_file (string)
Path to the data file containing the metal cooling and UV background tables. Default: “”.
Gamma (float)
See Enzo equivalent above. Default: 5/3.
ThreeBodyRate (int) [mapped to Grackle parameter three_body_rate]
See Enzo equivalent above. Default: 0.
CIECooling (int) [mapped to Grackle parameter cie_cooling]
See Enzo equivalent above. Default: 0.
H2OpticalDepthApproximation (int) [mapped to Grackle parameter h2_optical_depth_approximation]
See Enzo equivalent above. Default: 0.
PhotoelectricHeating (int) [mapped to Grackle parameter photoelectric_heating]
See Enzo equivalent above. Default: 0.
PhotoelectricHeatingRate (float) [mapped to Grackle parameter photoelectric_heating_rate]
See Enzo equivalent above. Default: 8.5e-26.
Compton_xray_heating (int)
Flag to enable Compton heating from an X-ray background following Madau & Efstathiou (1999). Default: 0.
LWbackground_intensity (float)
Intensity of a constant Lyman-Werner H2 photo-dissociating radiation field in units of 10-21 erg s-1 cm-2 Hz-1 sr-1. Default: 0.
LWbackground_sawtooth_suppression (int)
Flag to enable suppression of Lyman-Werner flux due to Lyman-series absorption (giving a sawtooth pattern), taken from Haiman & Abel, & Rees (2000). Default: 0.

## Particle Parameters¶

ParticleBoundaryType (external)
The boundary condition imposed on particles. At the moment, this parameter is largely ceremonial as there is only one type implemented: periodic, indicated by a 0 value. Default: 0
ParticleCourantSafetyNumber (external)
This somewhat strangely named parameter is the maximum fraction of a cell width that a particle is allowed to travel per timestep (i.e. it is a constant on the timestep somewhat along the lines of it’s hydrodynamic brother). Default: 0.5
NumberOfParticles (obsolete)
Currently ignored by all initializers, except for TestGravity and TestGravitySphere where it is the number of test points. Default: 0
NumberOfParticleAttributes (internal)
It is set to 3 if either StarParticleCreation or StarParticleFeedback is set to 1 (TRUE). Default: 0
ParallelParticleIO (external)
Normally, for the mpi version, the particle data are read into the root processor and then distributed to separate processors. However, for very large number of particles, the root processor may not have enough memory. If this toggle switch is set on (i.e. to the value 1), then Ring i/o is turned on and each processor reads its own part of the particle data. More I/O is required, but it is more balanced in terms of memory. ParallelRootGridIO and ParallelParticleIO MUST be set for runs involving > 64 cpus! See also ParallelRootGridIO in I/O Parameters. Default: 0 (FALSE).
ParticleSplitterIterations (external)
Set to 1 to split particles into 13 particles (= 12 children+1 parent, Kitsionas & Whitworth (2002)). This should be ideal for setting up an low-resolution initial condition for a relatively low computational cost, running it for a while, and then restarting it for an extremely high-resolution simulation in a focused region. Currently it implicitly assumes that only DM (type=1) and conventional star particles (type=2) inside the RefineRegion get split. Other particles, which usually become Star class objects, seem to have no reason to be split. It is reset to zero after a restart to avoid resplitting in subsequent datasets. It can be set to a maximum of 4. Default: 0
ParticleSplitterRandomSeed (external)
Random seed used when randomly rotating the hexagonal close packed array on whose vertices the split particles are placed. Default: 131180
ParticleSplitterMustRefine (external)
Set to 1 to mark the split particles as must-refine particles. The user must also set associated must-refine parameters to enable its machinery that can be used to restrict AMR only to the must-refine particles. Default: 0
ParticleSplitterMustRefineIDFile (external)

Filename for the HDF5 file that has a dataset containing the particle IDs that should be marked as must-refine. All other particles within the region marked for splitting will retain their original types. If not set, all particles within the must-refine region will be must-refine particles. This must be used in conjunction with ParticleSplitterMustRefine = 1. The dataset must be named particle_identifier in the base group. Default: (null).

An example yt script is provided below, selecting the particles in a sphere centered at [0.5, 0.5, 0.5] with a radius 0.05 in code length units.

import yt
import h5py as h5

center = ds.arr([0.5, 0.5, 0.5], 'code_length')
fp = h5.File('particle-ids.h5', 'w')
fp['particle_identifier'] = sp['particle_index'].astype('int')
fp.close()

ParticleSplitterFraction (external)
An array of four values that represent the width of the splitting region in units of the original refine region set by RefineRegionLeftEdge and RefineRegionRightEdge. The splitting region is centered on the refine region center. Each successive value represents the next nested split region. Valid up to ParticleSplitterIterations times. Cannot be used with ParticleSplitterCenterRegion. Default: 1.0 (all 4 values)
ParticleSplitterCenter (external)
The center of split region in code units. Specify if the split region does not correspond to the center of the refine region. Not used if negative. Default: -1.0 -1.0 -1.0
ParticleSplitterCenterRegion (external)
The width of the split region in code units. Must be used in conjunction with ParticleSplitterCenter. Each successive value represents the next nested split region. Cannot be used with ParticleSplitterFraction. Valid up to ParticleSplitterIterations times. Not used if negative. Default: -1.0 (all 4 values)
ParticleSplitterChildrenParticleSeparation (external)
This is the spacing between the child particles placed on a hexagonal close-packed (HCP) array. In units of a cell size which the parent particle resides in. Default: 1.0

## Star Formation and Feedback Parameters¶

For details on each of the different star formation methods available in Enzo see Star, Black Hole and Sink Particles.

### General Star Formation¶

StarParticleCreation (external)
This parameter is bitwise so that multiple types of star formation routines can be used in a single simulation. For example if methods 1 and 3 are desired, the user would specify 10 (21 + 23), or if methods 1, 4 and 7 are wanted, this would be 146 (21 + 24 + 27). Default: 0
0  - Cen & Ostriker (1992)
1  - Cen & Ostriker (1992) with stocastic star formation
2  - Global Schmidt Law / Kravstov et al. (2003)
3  - Population III stars / Abel, Wise & Bryan (2007)
4  - Sink particles: Pure sink particle or star particle with wind feedback depending on
choice for HydroMethod / Wang et al. (2009)
5  - Radiative star clusters  / Wise & Cen (2009)
6  - [reserved for future use]
7  - Cen & Ostriker (1992) with no delay in formation
8  - Springel & Hernquist (2003)
9  - Massive Black Hole (MBH) particles insertion by hand / Kim et al. (2010)
10 - Population III stellar tracers
11 - Molecular hydrogen regulated star formation
13 - Distributed stellar feedback model (So et al. 2014)
14 - Cen & Ostriker (1992) stochastic star formation with kinetic feedback
/ Simpson et al. (2015)

StarParticleFeedback (external)
This parameter works the same way as StarParticleCreation but only is valid for StarParticleCreation method = 0, 1, 2, 7, 8 and 14 because methods 3, 5 and 9 use the radiation transport module and Star_*.C routines to calculate the feedback, 4 has explicit feedback and 10 does not use feedback. Default: 0.
StarFeedbackDistRadius (external)
If this parameter is greater than zero, stellar feedback will be deposited into the host cell and neighboring cells within this radius. This results in feedback being distributed to a cube with a side of StarFeedbackDistRadius+1. It is in units of cell widths of the finest grid which hosts the star particle. Only implemented for StarParticleCreation method = 0 or 1 with StarParticleFeedback method = 1. (If StarParticleFeedback = 0, stellar feedback is only deposited into the cell in which the star particle lives). Default: 0.
StarFeedbackDistCellStep (external)
In essence, this parameter controls the shape of the volume where the feedback is applied, cropping the original cube. This volume that are within StarFeedbackDistCellSteps cells from the host cell, counted in steps in Cartesian directions, are injected with stellar feedback. Its maximum value is StarFeedbackDistRadius * TopGridRank. Only implemented for StarParticleCreation method = 0 or 1 with StarParticleFeedback method = 1. See Distributed Stellar Feedback for an illustration. Default: 0.
StarMakerUseJeansMass (external)
This parameter controls the usage of the Jeans Mass check for star formation. When spatial resolution gets high enough to resolve the Jeans length, the Jeans Mass check restricts star formation that should occur. Only implemented for StarParticleCreation method = 1 (e.g. star_marker_2). Default: 1.
StarMakerTypeIaSNe (external)
This parameter turns on thermal and chemical feedback from Type Ia supernovae. The mass loss and luminosity of the supernovae are determined from fits of K. Nagamine. The ejecta are traced in a separate species field, MetalSNIa_Density. The metallicity of star particles that comes from this ejecta is stored in the particle attribute typeia_fraction. Can be used with StarParticleCreation method = 0, 1, 2, 5, 7, 8, and 13. Default: 0.
StarMakerPlanetaryNebulae (external)
This parameter turns on thermal and chemical feedback from planetary nebulae. The mass loss and luminosity are taken from the same fits from K. Nagamine. The chemical feedback injects gas with the same metallicity as the star particle, and the thermal feedback equates to a 10 km/s wind. The ejecta are not stored in its own species field. Can be used with StarParticleCreation method = 0, 1, 2, 5, 7, 8, and 13. Default: 0.
StarParticleRadiativeFeedback (external)
By setting this parameter to 1, star particles created with methods (0, 1, 2, 5, 7, 8, 13) will become radiation sources with the UV luminosity being determined with the parameter StarEnergyToStellarUV. Default: OFF

### Normal Star Formation¶

The parameters below are considered in StarParticleCreation method 0, 1, 2, 7, 8, 13 and 14.

StarMakerOverDensityThreshold (external)
The overdensity threshold in code units (for cosmological simulations, note that code units are relative to the total mean density, not just the dark matter mean density) before star formation will be considered. For StarParticleCreation method = 7 in cosmological simulations, however, StarMakerOverDensityThreshold should be in particles/cc, so it is not the ratio with respect to the DensityUnits (unlike most other star_makers). This way one correctly represents the Jeans collapse and molecular cloud scale physics even in cosmological simulations. Default: 100
StarMakerSHDensityThreshold (external)
The critical density of gas used in Springel & Hernquist star formation ( \rho_{th} in the paper) used to determine the star formation timescale in units of g cm-3. Only valid for StarParticleCreation method = 8. Default: 7e-26.
StarMakerMassEfficiency (external)
The fraction of identified baryonic mass in a cell (Mass*dt/t_dyn) that is converted into a star particle. Default: 1
StarMakerMinimumMass (external)
The minimum mass of star particle, in solar masses. Note however, the star maker algorithm 2 has a (default off) “stochastic” star formation algorithm that will, in a pseudo-random fashion, allow star formation even for very low star formation rates. It attempts to do so (relatively successfully according to tests) in a fashion that conserves the global average star formation rate. Default: 1e9
StarMakerMinimumDynamicalTime (external)
When the star formation rate is computed, the rate is proportional to M_baryon * dt/max(t_dyn, t_max) where t_max is this parameter. This effectively sets a limit on the rate of star formation based on the idea that stars have a non-negligible formation and life-time. The unit is years. Default: 1e6
StarMakerTimeIndependentFormation (external)
When used, the factor of dt / t_dyn is removed from the calculation of the star particle mass above. Instead of the local dynamical time, the timescale over which feedback occurs is a constant set by the parameter StarMakerMinimumDynamicalTime. This is necessary when running with conduction as the timesteps can be very short, which causes the calculated star particle mass to never exceed reasonable values for StarMakerMinimumMass. This prevents cold, star-forming gas from actually forming stars, and when combined with conduction, results in too much heat being transferred out of hot gas. When running a cosmological simulation with conduction and star formation, one must use this otherwise bad things will happen. (1 - ON; 0 - OFF) Default: 0.
StarMassEjectionFraction (external)
The mass fraction of created stars which is returned to the gas phase. Default: 0.25
StarMetalYield (external)
The mass fraction of metals produced by each unit mass of stars created (i.e. it is multiplied by mstar, not ejected). Default: 0.02
StarEnergyToThermalFeedback (external)
The fraction of the rest-mass energy of the stars created which is returned to the gas phase as thermal energy. Default: 1e-5
StarEnergyToStellarUV (external)
The fraction of the rest-mass energy of the stars created which is returned as UV radiation with a young star spectrum. This is used when calculating the radiation background. Default: 3e-6
StarEnergyToQuasarUV (external)
The fraction of the rest-mass energy of the stars created which is returned as UV radiation with a quasar spectrum. This is used when calculating the radiation background. Default: 5e-6
StarFeedbackKineticFraction (external)
Only valid for StarParticleFeedback method = 14. If set to a zero or positive value between 0.0 and 1.0, this is the constant fraction of energy injected in kinetic form. If set to -1, then a variable kinetic fraction is used that depends on local gas density, metallicity and resolution. See Simpson et al. 2015 for details. Note, some failures may occur in -1 mode. Default 0.0
StarMakerExplosionDelayTime (external)
Only valid for StarParticleFeedback method = 14. If set to a positive value, energy, metals and mass from the particle are injected in a single timestep that is delayed from the particle creation time by this amount. This value is in units of Myrs. If set to a negative value, energy, mass and metals are injected gradually in the same way as is done for StarParticleFeedback method = 1. Default -1.
StarMakerMinimumMassRamp (external)
Sets the Minimum Stellar Mass (otherwise given by StarMakerMinimumMass to ramp up over time, so that a small mass can be used early in the calculation and a higher mass later on, or vice versa. The minimum mass is “ramped” up or down starting at StarMakerMinimumMassRampStartTime and ending at StarMakerMinimumMassRampEndTime. The acceptable values are: (1) linear evolution of mass in time (2) linear evolution of mass in redshift (3) exponential evolution of mass in time (4) exponential evolution of mass in redshift
StarMakerMinimumMassRampStartTime (external)
The code unit time, or redshift, to start the ramp of the StarMakerMinimumMass Before this time the minimum mass will have a constant value given by StarMakerMinimumMassRampStartMass
StarMakerMinimumMassRampEndTime (external)
The code unit time, or redshift, to start the ramp of the StarMakerMinimumMass After this time the minimum mass will have a constant value given by StarMakerMinimumMassRampEndMass
StarMakerMinimumMassRampStartMass (external)
The mass at which to start the ramp in the minimum stellar mass. This mass will be used at all times before StarMakerMinimumMassRampStartTime as well.
StarMakerMinimumMassRampEndMass (external)
The mass at which to end the ramp in the minimum stellar mass. This mass will be used at all times after StarMakerMinimumMassRampEndTime as well.

### Molecular Hydrogen Regulated Star Formation¶

The parameters below are considered in StarParticleCreation method 11.

H2StarMakerEfficiency (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerNumberDensityThreshold (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerMinimumMass (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerMinimumH2FractionForStarFormation (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerStochastic (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerUseSobolevColumn (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerSigmaOverR (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerAssumeColdWarmPressureBalance (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerH2DissociationFlux_MW (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerH2FloorInColdGas (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
H2StarMakerColdGasTemperature (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.
StarFormationOncePerRootGridTimeStep (external)
See Method 11: Molecular Hydrogen Regulated Star Formation.

### Population III Star Formation¶

The parameters below are considered in StarParticleCreation method 3.

PopIIIStarMass (external)
Stellar mass of Population III stars created in StarParticleCreation method 3. Units of solar masses. The luminosities and supernova energies are calculated from Schaerer (2002) and Heger & Woosley (2002), respectively.
PopIIIBlackHoles (external)
Set to 1 to create black hole particles that radiate in X-rays for stars that do not go supernova (< 140 solar masses and > 260 solar masses). Default: 0.
PopIIIBHLuminosityEfficiency (external)
The radiative efficiency in which the black holes convert accretion to luminosity. Default: 0.1.
PopIIIOverDensityThreshold (external)
The overdensity threshold (relative to the total mean density) before Pop III star formation will be considered. Default: 1e6.
PopIIIH2CriticalFraction (external)
The H_2 fraction threshold before Pop III star formation will be considered. Default: 5e-4.
PopIIIMetalCriticalFraction (external)
The metallicity threshold (relative to gas density, not solar) before Pop III star formation will be considered. Note: this should be changed to be relative to solar! Default: 1e-4.
PopIIISupernovaRadius (external)
If the Population III star will go supernova (140<M<260 solar masses), this is the radius of the sphere to inject the supernova thermal energy at the end of the star’s life. Units are in parsecs. Default: 1.
PopIIISupernovaUseColour (external)
Set to 1 to trace the metals expelled from supernovae. If using HydroMethod 3 or 4, also set MixSpeciesAndColors to 1 to trace metals. Default: 0.
PopIIIUseHypernovae (external)
Set to 1 to use the hypernova energies and metal ejecta masses from Nomoto et al. (2006). If set to 0, then the supernova energies are always 1e51 erg but use the supernova metal ejecta masses from Nomoto et al. (2006). Default: 1
PopIIISupernovaExplosions (external)
Set to 1 to consider supernovae from Pop III stars. Set to 0 to neglect all Pop III supernovae, regardless of their masses. Default: 1
PopIIIInitialMassFunction (external)
When turned on, each Pop III stellar mass is randomly drawn from an IMF that is Salpeter above some characteristic mass and exponentially cutoff below this mass. Default: 0
PopIIIInitialMassFunctionSeed (external)
Random initial seed for the Pop III stellar mass randomizer. Default: INT_UNDEFINED
PopIIILowerMassCutoff (external)
Lower limit of the Pop III IMF. Default: 1
PopIIIUpperMassCutoff (external)
Upper limit of the Pop III IMF. Default: 300
PopIIIInitialMassFunctionSlope (external)
Slope of the Salpeter (high-mass) portion of the Pop III IMF. Default: -1.3
PopIIIInitialMassFunctionCalls (internal)
Number of times a Pop III mass has been drawn from the IMF. Used for restarts and reproducibility. Default: 0
PopIIISupernovaMustRefine (external)
When turned on, the region around a star about to go supernova is refined to the maximum AMR level. Experimental. Default: 0
PopIIISupernovaMustRefineResolution (external)
Used with PopIIISupernovaMustRefine. Minimum number of cells across the blastwave. Default: 32
PopIIIHeliumIonization (external)
When turned on, Pop III stars will emit helium singly- and doubly-ionizing radiation. Default: 0
PopIIIColorDensityThreshold (external)
Above this density, a Pop III “color” particle forms, and it will populate the surrounding region with a color field. Units: mean density. Default: 1e6
PopIIIColorMass (external)
A Pop III “color” particle will populate the surrounding region with a mass of PopIIIColorMass. Units: solar masses. Default: 1e6

The parameters below are considered in StarParticleCreation method 5.

StarClusterMinDynamicalTime (external)
When determining the size of a star forming region, one method is to look for the sphere with an enclosed average density that corresponds to some minimum dynamical time. Observations hint that this value should be a few million years. Units are in years. Default: 1e7.
StarClusterIonizingLuminosity (external)
The specific luminosity of the stellar clusters. In units of ionizing photons per solar mass. Default: 1e47.
StarClusterSNEnergy (external)
The specific energy injected into the gas from supernovae in the stellar clusters. In units of ergs per solar mass. Default: 6.8e48 (Woosley & Weaver 1986).
StarClusterSNRadius (external)
This is the radius of the sphere to inject the supernova thermal energy in stellar clusters. Units are in parsecs. Default: 10.
StarClusterFormEfficiency (external)
Fraction of gas in the sphere to transfer from the grid to the star particle. Recall that this sphere has a minimum dynamical time set by StarClusterMinDynamicalTime. Default: 0.1.
StarClusterMinimumMass (external)
The minimum mass of a star cluster particle before the formation is considered. Units in solar masses. Default: 1000.
StarClusterCombineRadius (external)
It is possible to merge star cluster particles together within this specified radius. Units in parsecs. This is probably not necessary if ray merging is used. Originally this was developed to reduce the amount of ray tracing involved from galaxies with hundreds of these radiating particles. Default: 10.
StarClusterUseMetalField (external)
Set to 1 to trace ejecta from supernovae. Default: 0.
StarClusterHeliumIonization (external)
When turned on, stellar clusters will emit helium singly- and doubly-ionizing radiation. Default: 0
StarClusterRegionLeftEdge (external)
Can restrict the region in which star clusters can form. Origin of this region. Default: 0 0 0
StarClusterRegionRightEdge (external)
Can restrict the region in which star clusters can form. Right corner of this region. Default: 1 1 1
StarClusterUnresolvedModel (external)
Regular star clusters live for 20 Myr, but this is only valid when molecular clouds are resolved. When this parameter is on, the star formation rate is the same as the Cen & Ostriker exponential rate. Default: 0

### Massive Black Hole Particle Formation¶

The parameters below are considered in StarParticleCreation method 9.

MBHInsertLocationFilename (external)

The mass and location of the MBH particle that has to be inserted. For example, the content of the file should be in the following form. For details, see mbh_maker.src. Default: mbh_insert_location.in

#order: MBH mass (in Ms), MBH location[3], MBH creation time
100000.0      0.48530579      0.51455688      0.51467896      0.0


### Sink Formation and Feedback¶

The parameters below are considered in sink creation routines: sink_maker, star_maker8, star_maker9 (and occasionally only in certain set-ups). Because many of the following parameters are not actively being tested and maintained, users are encouraged to carefully examine the code before using it.

AccretionKernal (external)
While this parameter is used to determine the accretion kernel in star_maker8.C, there is no choice other than 1 at the moment: Ruffert, ApJ (1994) 427 342 (a typo in the parameter name…). Default: 0
StellarWindFeedback (external)
This parameter is used to turn on sink particle creation by star_maker8.C and also its feedback. Currently implemented are: 1 - protostellar jets along the magnetic fields, 2 - protostellar jets along random directions, 3 - isotropic main sequence stellar wind, 4 - not implemented, 5 - not implemented, 6 - methods 2 and 3 combined. Default: 0
StellarWindTurnOnMass (external)
This parameter is used to decide whether mass increase reached the ejection threshold for StellarWindFeedback=1, 2, or 6 in star_maker8.C. Default: 0.1
MSStellarWindTurnOnMass (external)
This parameter is used to decide whether mass increase reached the ejection threshold for StellarWindFeedback = 3 or 6 in star_maker8.C. Default: 10.0
BigStarFormation (external)
This parameter is used to turn on sink particle creation by star_maker9.C.
BigStarFormationDone (external)
In star_maker9.C, this parameter is used when we do not want to form BigStars any more.
BigStarSeparation (external)
In star_maker[89].C, if the newly-created sink particle is within a certain distance from the closest pre-existing sink, then add to it rather than creating a new one.
SinkMergeDistance
[not used]
SinkMergeMass
[not used]

### Magnetic Supernova Feedback¶

The parameters below are currently considered in StarParticleCreation methods 0 and 1.

UseMagneticSupernovaFeedback (external)
This parameter is used to turn on magnetic supernova feedback. Currently implemented values are: 1 - the user needs to specify the desired supernova radius and duration. If none are specified, the default values will be used (see below), 2 - the supernova radius and duration will be calculated during runtime based on the grid resolution and timestep. Default: 0
MagneticSupernovaEnergy (external)
The total amount of magnetic energy to be injected by a single supernova event (in units of ergs). Default: 1e51
MagneticSupernovaRadius (external)
The radius of the sphere (in parsecs) over which to inject supernova energy. This value should be at least 1.5 times the minimum cell width in the simulation. Default: 300
MagneticSupernovaDuration (external)
The duration (in years) over which the total magnetic supernova energy is injected. This should be set to at least 5 times the minimum timestep of the simulation. Default: 5e4

## Active Particles¶

To allow for the creation of an active particle the following line must be added to the parameter file or restart file: AppendActiveParticleType = <ActiveParticleType> See Active Particles for the types of active particles that exist.

## SmartStar Parameters¶

### SmartStar Accretion¶

SmartStarAccretion (external)

Set to 1 to turn on spherical Bondi-Hoyle accretion based on the formalisms presented in Krumholz et al. (2004)

Set to 4 to turn on angular momentum limited accretion based on the formalism adopted by Rosas-Guevara et al. (2015).

Set to 5 to again turn on spherical Bondi-Hoyle accretion but this time the formalism includes a correction which accounts for the vorticity of the gas based on Krumholz et al. (2005).

Set to 6 to use the viscous angular momentum prescription from DeBuhr et al. (2010).

Set to 7 to use a modified accretion rate based on the alpha-disk model of Shakura & Sunyaev (1973) This scheme is based on Cen et al..

Set to 8 to employ the converging mass flux approach. This is not based on any indirect properties of the gas as above and simply measures the flow of gas through the accetion radius of the SmartStar. It is based on the accretion mechanism used by Bleuler in Ramses and in Enzo by Regan et al. (2018, 2019).

Default: 8

Accretion is never capped by default but can be capped at the Eddington rate as notes below.

### SmartStar Feedback¶

SmartStarFeedback (external)
This is the master feedback parameter. Set this to 0 and all feedback is turned off. It’s a master switch. Switch it to 1 and then feedback is on but needs to be fine grained by more detailed parameters below. Default: 0
SmartStarStellarRadiativeFeedback (external)
This parameter controls whether stellar feedback is activated or not. For feedback from PopIII or SMSs then this needs to be on. The stellar radiative feedback is divided up into 5 energy bins. The energy bins have energies of 2.0 eV, 12.8 eV, 14.0 eV, 25.0 eV and 200 eV. The fraction of energy assigned to each bin is determined using the PopIII tables from Schaerer et. al 2002 Table 4. The spectrum for a PopIII star and SMS are different. For a PopIII star a spectrum for a 40 Msolar star is assumed and weighted accordingly. For a SMS a 1000 Msolar star is assumed and weighted accordingly. Future improvements to the SEDs employed here are under active investigation. Default: 0
SmartStarBHFeedback (external)
This is a master switch on black hole feedback. Must be turned on if you want black hole feedback. Default: 0
SmartStarBHRadiativeFeedback (external)
This parameter controls whether black hole radiative feedback gets turned on or not. When turned on the radiative feedback from a black hole depends both on the mass of the black hole and the accretion rate onto the black hole. Both of these quantities are captured and stored as part of the SmartStar. Details of the SED used can be found in the appendix of Regan et al. 2019 and is made from assuming a multi-colour disk for the accretion disk and a corona fit by a power law. The radiation emitted by the accretion disk is hard-coded is be emitted by 5 bins with energies of 2.0 eV, 12.8 eV, 19.1 eV, 217.3 eV and 5190 eV. The fraction of energy assigned to each bin is then determined by the mass of the black hole and the associated accretion rate at a given time. The formalism is valid for black hole masses between 1 Msolar and 1e9 Msolar and for accretion rates between 1e-6 Msolar/yr and 1e3 Msolar/yr. Default: 0
SmartStarBHThermalFeedback (external)
This parameter controls whether the black hole thermal feedback gets turned. Thre thermal energy is generated by feedback through the accretion process. If this is turned on then the SmartStarBHRadiativeFeedback should presumably be turned off unless you have a good reason to include both. The efficiency, epsilon, depends on both the spin of the black hole and the ISCO oribit. In order to calculate this accurately Eqn 32 from Abromowicz & Fragile (2013) is used. See ActiveParticle_SmartStar.h. The feedback is released iostropically in a sphere surrounding the SmartStar particle. Default: 0
SmartStarBHJetFeedback (external)
The methodology for this algorithm is based on that of Kim et. al (2011). Jets can be activated when a spinning black hole is accreting. The jets are bipolar and are set along the angular momentum vector of the SmartStar. The velocity of the jet(s) is set by a separate parameter below. No other parameters need to be set to activate the jet. Default: 0
SmartStarEddingtonCap (external)
This parameter allows for accretion onto the SmartStar to be capped at the Eddington limit. Default: 0
SmartStarSpin (external)
The dimensionless spin of the SmartStar particle. This is a very unconstrained parameter and cannot be readily computed on the fly. This parameter should be set if you want to have jet feedback. Setting this is zero and turning on jet feedback wouldn’t make sense. The default is set to be 0.7 and this is probably reasonable. Default: 0.7
SmartStarSMSLifetime (external)
This is the lifetime for a supermassive star in years. After this time has elapsed a SmartStar particle which is behaving like a SMS will collapse directly into a black hole with no supernova event. Default: 1e6
SmartStarJetVelocity (external)
The velocity that the jets are ejected at. Typically jets are observed to travel at a substantial fraction of the speed of light - especially those ejected during periods of high accretion. However, as mass gets entrained in the jet it slows down. The units of this parameter are as a fraction of the speed of light. Default: 0.1
SmartStarFeedbackJetsThresholdMass (external)
Jets are only ejected once this amount of mass is available for ejection after an accretion event. Therefore, if there is very limited accretion and this parameter is set high then jets will be very infrequent. In units of solar masses. Default: 1.0
SmartStarSuperEddingtonAdjustment (external)
As accretion rates exceed the canonical Eddington rate the radiative efficiency of the feedback changes. We use the fits from Madau et al. to adjust the efficiency when accretion enters the super-critical regime. The fits are based on the slim-disk model of accretion which generates inefficient feedback. Default: 1

RadiationFieldType (external)
This integer parameter specifies the type of radiation field that is to be used. Except for RadiationFieldType = 9, which should be used with MultiSpecies = 2, UV backgrounds can currently only be used with MultiSpecies = 1 (i.e. no molecular H support). The following values are used. For field type 15, see Table 3 in Haardt & Madau (2012). Default: 0
1  - Haardt & Madau spectrum with q_alpha = 1.5
2  - Haardt & Madau spectrum with q_alpha = 1.8
3  - Modified Haardt & Madau spectrum to match observations
(Kirkman & Tytler 2005).
4  - Haardt & Madau spectrum with q_alpha = 1.5 supplemented with an X-ray Compton heating
background from Madau & Efstathiou (see astro-ph/9902080)
9  - Constant molecular H2 photo-dissociation rate
10 - Internally computed radiation field using the algorithm of Cen & Ostriker
11 - Same as previous, but with very, very simple optical shielding fudge
12 - Haardt & Madau spectrum with q_alpha = 1.57
15 - Haardt & Madau 2012.

RadiationFieldLevelRecompute (external)
This integer parameter is used only if the previous parameter is set to 10 or 11. It controls how often (i.e. the level at which) the internal radiation field is recomputed. Default: 0
RadiationSpectrumNormalization (external)
This parameter was initially used to normalize the photo-ionization and photo-heating rates computed in the function RadiationFieldCalculateRates() and then passed on to the calc_photo_rates(), calc_rad() and calc_rates() routines. Later, the normalization as a separate input parameter was dropped for all cases by using the rates computed in RadiationFieldCalculateRates() with one exception: The molecular hydrogen (H2) dissociation rate. There a normalization is performed on the rate by multiplying it with RadiationSpectrumNormalization. Default: 1e-21
RadiationShield (external)
This parameter specifies whether the user wants to employ approximate radiative-shielding. This parameter will be automatically turned on when RadiationFieldType is set to 11. When set to 1, it calculates shielding for H/He. See calc_photo_rates.src for more details. When set to 2, it shields only H2 with the Sobolev-like approximation from Wolcott-Green et al. (2011). Default: 0
RadiationFieldRedshift (external)
This parameter specifies the redshift at which the radiation field is calculated. If a UV radiation background is used in a non-cosmological simulation, this needs to be defined. Negative redshifts are permitted. Default: (undefined)
RadiationRedshiftOn (external)
The redshift at which the UV background turns on. Default: 7.0.
RadiationRedshiftFullOn (external)
The redshift at which the UV background is at full strength. Between z = RadiationRedshiftOn and z = RadiationRedshiftFullOn, the background is gradually ramped up to full strength. Default: 6.0.
RadiationRedshiftDropOff (external)
The redshift at which the strength of the UV background is begins to gradually reduce, reaching zero by RadiationRedshiftOff. Default: 0.0.
RadiationRedshiftOff (external)
The redshift at which the UV background is fully off. Default: 0.0.
TabulatedLWBackground (external)
When on, the amplitude of the Lyman-Werner background is read from the file LW_J21.in as a function of redshift. Each line should have the redshift and LW background in units of 1e-21 erg/cm^3/s/Hz/sr. Default: 0
AdjustUVBackground (external)
AdjustUVBackgroundHighRedshift (external)
SetUVAmplitude (external)
SetHeIIHeatingScale (external)
RadiationSpectrumSlope (external)

### Radiative Transfer (Ray Tracing) Parameters¶

RadiativeTransfer (external)
Set to 1 to turn on the adaptive ray tracing following Abel, Wise & Bryan 2007. Note that Enzo must be first recompiled after setting make photon-yes. Default: 0.
RadiativeTransferRadiationPressure (external)
Set to 1 to turn on radiation pressure created from absorbed photon packages. Default: 0
RadiativeTransferInitialHEALPixLevel (external)
Chooses how many rays are emitted from radiation sources. The number of rays in Healpix are given through # = 12x4level. Default: 3.
RadiativeTransferRaysPerCell (external)
Determines the accuracy of the scheme by giving the minimum number of rays to cross cells. The more the better (slower). Default: 5.1.
RadiativeTransferSourceRadius (external)
The radius at which the photons originate from the radiation source. A positive value results in a radiating sphere. Default: 0.
RadiativeTransferPropagationRadius (external)
The maximum distance a photon package can travel in one timestep. Currently unused. Default: 0.
RadiativeTransferPropagationSpeed (external)
The fraction of the speed of light at which the photons travel. Default: 1.
RadiativeTransferCoupledRateSolver (external)
Set to 1 to calculate the new ionization fractions and gas energies after every radiative transfer timestep. This option is highly recommended to be kept on. If not, ionization fronts will propagate too slowly. Default: 1.
RadiativeTransferOpticallyThinH2 (external)
Set to 1 to include an optically-thin H_2 dissociating (Lyman-Werner) radiation field. This also causes the HM and H2II to be dissociated in an opticall thin fashion. Only used if MultiSpecies > 1. If MultiSpecies > 1 and this option is off, the Lyman-Werner radiation field will be calculated with ray tracing. Default: 1.
RadiativeTransferOpticallyThinH2CharLength (external)
This parameter controls the length over which the Jeans length self shielding prescription is performed. The default value is 0.25 which means that the characteristic length for applying self shielding of LW photons is over one quarter of the Jeans length. Leaving at this value is probably a good idea unless there is a strong reason to modify it. Default: 0.25.
RadiativeTransferSplitPhotonPackage (external)
Once photons are past this radius, they can no longer split. In units of kpc. If this value is negative (by default), photons can always split. Default: FLOAT_UNDEFINED.
RadiativeTransferHubbleTimeFraction (external)
Photon packages are deleted when its associated photo-ionization timescale, considering the limit when all photons are absorbed in one cell, drops below a fraction (this parameter) of a Hubble time. This parameter can be safely set to 0.01 when ray merging is used. Default: 0.1
RadiativeTransferFluxBackgroundLimit (external)
When the flux of a photon package drops below a fraction (this parameter) of the background radiation field, the ray is deleted. Only used with ray merging. Default: 0.01
RadiativeTransferPhotonEscapeRadius (external)
The number of photons that pass this distance from its source are summed into the global variable EscapedPhotonCount[]. This variable also keeps track of the number of photons passing this radius multiplied by 0.5, 1, and 2. Units are in kpc. Not used if set to 0. Default: 0.
RadiativeTransferSourceClustering (external)
Set to 1 to turn on ray merging from combined virtual sources on a binary tree. Default: 0.
RadiativeTransferOpticallyThinSourceClustering (external)
Set to 1 to use the above tree when computing optically thin radiation (RadiativeTransferSourceClustering must be set to 1), which can greatly reduce computational time for many sources / large cell counts. If on, this source clustering is only used when the number of sources is greater than ten. Testing in idealized galaxy simulations has shown that this should be used with some caution. Its behavior is sensitive to the value of RadiativeTransferPhotonMergeRadius. Larger values tend to significantly underestimate radiation near individual sources; it is recommended to first try and use values around 3. Default: 0
RadiativeTransferPhotonMergeRadius (external)
The radius at which the rays will merge from their SuperSource, which is the luminosity weighted center of two sources. This radius is in units of the separation of two sources associated with one SuperSource. If set too small, there will be angular artifacts in the radiation field. Default: 3.0
RadiativeTransferSourceBeamAngle (external)
Rays will be emitted within this angle in degrees of the poles from sources with “Beamed” types. Default: 30
RadiativeTransferPeriodicBoundary (external)
Set to 1 to turn on periodic boundary conditions for photon packages. Default: 0.
RadiativeTransferTimestepVelocityLimit (external)
Limits the radiative transfer timestep to a minimum value that is determined by the cell width at the finest level divided by this velocity. Units are in km/s. Default: 100.
RadiativeTransferTimestepVelocityLevel (external)
Limit the ray tracing timestep by a sound crossing time (see RadiativeTransferTimestepVelocityLimit) across a cell on the level specified with this parameter. Not used if equal to INT_UNDEFINED (-99999). Default: INT_UNDEFINED
RadiativeTransferHIIRestrictedTimestep (external)
Adaptive ray tracing timesteps will be restricted by a maximum change of 10% in neutral fraction if this parameter is set to 1. If set to 2, then the incident flux can change by a maximum of 0.5 between cells. See Wise & Abel (2011) in Sections 3.4.1 and 3.4.4 for more details. Default: 0
RadiativeTransferAdaptiveTimestep (external)
Must be 1 when RadiativeTransferHIIRestrictedTimestep is non-zero. When RadiativeTransferHIIRestrictedTimestep is 0, then the radiative transfer timestep is set to the timestep of the finest AMR level. Default: 0
RadiativeTransferLoadBalance (external)
When turned on, the grids are load balanced based on the number of ray segments traced. The grids are moved to different processors only for the radiative transfer solver. Default: 0
RadiativeTransferHydrogenOnly (external)
When turned on, the photo-ionization fields are only created for hydrogen. Default: 0
RadiativeTransferRayMaximumLength (external)
The maximum length that a ray is allowed to travel in box units. Thde default value is 1.7320608 (i.e. sqrt(3.0) so a ray covers the entire periodic region with some doubling up inevitably. Setting it to smaller value will reduce the computational cost. Default: 1.7320608
RadiativeTransferUseH2Shielding (external)
Should H2 self-shielding be used. Default: True
RadiativeTransferH2ShieldType (external)
If H2 shielding is turned on then which kind should we use. Setting this value to 0 used the self-shielding fit as per Draine & Bertoldi (1996). Setting this value to 1 uses the fit as per Wolcott-Green et al. (2011). Default: 0
RadiativeTransferH2IIDiss (external)
Should we also account for the photo-dissoication of H2II which occurs for radiation between 0.76eV and 13.6 eV. Default: True
RadiationXRaySecondaryIon (external)
Set to 1 to turn on secondary ionizations and reduce heating from X-ray radiation (Shull & van Steenberg 1985). Currently only BH and MBH particles emit X-rays. Default: 0.
RadiationXRayComptonHeating (external)
Set to 1 to turn on Compton heating on electrons from X-ray radiation (Ciotti & Ostriker 2001). Currently only BH and MBH particles emit X-rays. Default: 0.
RadiativeTransferInterpolateField (obsolete)
A failed experiment in which we evaluate the density at the midpoint of the ray segment in each cell to calculate the optical depth. To interpolate, we need to calculate the vertex interpolated density fields. Default: 0.
SimpleQ (external)
Ionizing photon luminosity of a “simple radiating source” that is independent of mass. In units of photons per second. Default: 1e50
SimpleRampTime (external)
Time to exponential ramp up the luminosity of a simple radiating source. In units of 1e6 years. Default: 0.1
RadiativeTransferTraceSpectrum (reserved)
reserved for future experimentation. Default: 0.
RadiativeTransferTraceSpectrumTable (reserved)
reserved for future experimentation. Default: spectrum_table.dat

RadiativeTransferFLD (external)

Set to 2 to turn on the fld-based radiation solvers following Reynolds, Hayes, Paschos & Norman, 2009. Note that you also have to compile the source using make photon-yes and a make hypre-yes. Note that if FLD is turned on, it will force RadiativeCooling = 0, GadgetEquilibriumCooling = 0, and RadiationFieldType = 0 to prevent conflicts. Default: 0.

IMPORTANT: Set RadiativeTransfer = 0 to avoid conflicts with the ray tracing solver above. Set RadiativeTransferOpticallyThinH2 = 0 to avoid conflicts with the built-in optically-thin H_2 dissociating field from the ray-tracing solver.

ImplicitProblem (external)
Set to 1 to turn on the implicit FLD solver, or 3 to turn on the split FLD solver. Default: 0.
RadHydroParamfile (external)
Names the (possibly-different) input parameter file containing solver options for the FLD-based solvers. These are described in the relevant User Guides, located in doc/implicit_fld and doc/split_fld. Default: NULL.
RadiativeTransferFLDCallOnLevel (reserved)
The level in the static AMR hierarchy where the unigrid FLD solver should be called. Currently only works for 0 (the root grid). Default: 0.
StarMakerEmissivityField (external)
When compiled with the FLD radiation transfer >make emissivity-yes; make hypre-yes, setting this to 1 turns on the emissivity field to source the gray radiation. Default: 0
uv_param (external)
When using the FLD radiation transfer and StarMakerEmissivityFIeld = 1, this is the efficiency of mass to UV light ratio. Default: 0

### Radiative Transfer (FLD) Implicit Solver Parameters¶

These parameters should be placed within the file named in RadHydroParamfile in the main parameter file. All are described in detail in the User Guide in doc/implicit_fld.
RadHydroESpectrum (external)
-1 - monochromatic spectrum at frequency h nu_{HI} = 13.6 eV
0  - power law spectrum, (nu / nu_{HI} )^(-1.5)
1  - T = 1e5 blackbody spectrum

RadHydroChemistry (external)
Use of hydrogen chemistry in ionization model, set to 1 to turn on the hydrogen chemistry, 0 otherwise. Default: 1.
RadHydroHFraction (external)
Fraction of baryonic matter comprised of hydrogen. Default: 1.0.
RadHydroModel (external)
Determines which set of equations to use within the solver. Default: 1.
1  - chemistry-dependent model, with case-B hydrogen II recombination coefficient.
2  - chemistry-dependent model, with case-A hydrogen II recombination coefficient.
4  - chemistry-dependent model, with case-A hydrogen II
recombination coefficient, but assumes an isothermal gas energy.
10 - no chemistry, instead uses a model of local thermodynamic
equilibrium to couple radiation to gas energy.

RadHydroMaxDt (external)
maximum time step to use in the FLD solver. Default: 1e20 (no limit).
RadHydroMinDt (external)
minimum time step to use in the FLD solver. Default: 0.0 (no limit).
RadHydroInitDt (external)
initial time step to use in the FLD solver. Default: 1e20 (uses hydro time step).
RadHydroDtNorm (external)
type of p-norm to use in estimating time-accuracy for predicting next time step. Default: 2.0.
 0 - use the max-norm.
>0 - use the specified p-norm.
<0 - illegal.

RadHydroDtRadFac (external)
Desired time accuracy tolerance for the radiation field. Default: 1e20 (unused).
RadHydroDtGasFac (external)
Desired time accuracy tolerance for the gas energy field. Default: 1e20 (unused).
RadHydroDtChemFac (external)
Desired time accuracy tolerance for the hydrogen I number density. Default: 1e20 (unused).
RadiationScaling (external)
Scaling factor for the radiation field, in case standard non-dimensionalization fails. Default: 1.0.
EnergyCorrectionScaling (external)
Scaling factor for the gas energy correction, in case standard non-dimensionalization fails. Default: 1.0.
ChemistryScaling (external)
Scaling factor for the hydrogen I number density, in case standard non-dimensionalization fails. Default: 1.0.
RadiationBoundaryX0Faces (external)
Boundary condition types to use on the x0 faces of the radiation field. Default: [0 0].
0 - Periodic.
1 - Dirichlet.
2 - Neumann.

RadiationBoundaryX1Faces (external)
Boundary condition types to use on the x1 faces of the radiation field. Default: [0 0].
RadiationBoundaryX2Faces (external)
Boundary condition types to use on the x2 faces of the radiation field. Default: [0 0].
RadHydroLimiterType (external)
Type of flux limiter to use in the FLD approximation. Default: 4.
0 - original Levermore-Pomraning limiter, à la Levermore & Pomraning, 1981 and Levermore, 1984.
1 - rational approximation to LP limiter.
2 - new approximation to LP limiter (to reduce floating-point cancellation error).
3 - no limiter.
4 - ZEUS limiter (limiter 2, but with no "effective albedo").

RadHydroTheta (external)
Time-discretization parameter to use, 0 gives explicit Euler, 1 gives implicit Euler, 0.5 gives trapezoidal. Default: 1.0.
RadHydroAnalyticChem (external)
Type of time approximation to use on gas energy and chemistry equations. Default: 1 (if possible for model).
0 - use a standard theta-method.
1 - use an implicit quasi-steady state (IQSS) approximation.

RadHydroInitialGuess (external)
Type of algorithm to use in computing the initial guess for the time-evolved solution. Default: 0.
0 - use the solution from the previous time step (safest).
1 - use explicit Euler with only spatially-local physics (heating & cooling).
2 - use explicit Euler with all physics.
5 - use an analytic predictor based on IQSS approximation of
spatially-local physics.

RadHydroNewtTolerance (external)
Desired accuracy for solution to satisfy nonlinear residual (measured in the RMS norm). Default: 1e-6.
RadHydroNewtIters (external)
Allowed number of Inexact Newton iterations to achieve tolerance before returning with FAIL. Default: 20.
RadHydroINConst (external)
Inexact Newton constant used in specifying tolerances for inner linear solver. Default: 1e-8.
RadHydroMaxMGIters (external)
Allowed number of iterations for the inner linear solver (geometric multigrid). Default: 50.
RadHydroMGRelaxType (external)

Relaxation method used by the multigrid solver. Default: 1.

:: 1 - Jacobi. 2 - Weighted Jacobi. 3 - Red/Black Gauss-Seidel (symmetric). 4 - Red/Black Gauss-Seidel (non-symmetric).

RadHydroMGPreRelax (external)
Number of pre-relaxation sweeps used by the multigrid solver. Default: 1.
RadHydroMGPostRelax (external)
Number of post-relaxation sweeps used by the multigrid solver. Default: 1.
EnergyOpacityC0, EnergyOpacityC1, EnergyOpacityC2, EnergyOpacityC3, EnergyOpacityC4 (external)
Parameters used in defining the energy-mean opacity used with RadHydroModel 10. Default: [1 1 0 1 0].
PlanckOpacityC0, PlanckOpacityC1, PlanckOpacityC2, PlanckOpacityC3, PlanckOpacityC4 (external)
Parameters used in defining the Planck-mean opacity used with RadHydroModel 10. Default: [1 1 0 1 0].

### Radiative Transfer (FLD) Split Solver Parameters¶

These parameters should be placed within the file named in RadHydroParamfile in the main parameter file. All are described in detail in the User Guide in doc/split_fld.
RadHydroESpectrum (external)
1  - T=1e5 blackbody spectrum
0  - power law spectrum, ( nu / nu_{HI})^(-1.5)
-1 - monochromatic spectrum at frequency h nu_{HI}= 13.6 eV
-2 - monochromatic spectrum at frequency h nu_{HeI}= 24.6 eV
-3 - monochromatic spectrum at frequency h nu_{HeII}= 54.4 eV

RadHydroChemistry (external)
Use of primordial chemistry in computing opacities and photo-heating/photo-ionization. Default: 1.
0 no chemistry
1 hydrogen chemistry
3 hydrogen and helium chemistry

RadHydroHFraction (external)
Fraction of baryonic matter comprised of hydrogen. Default: 1.0.
RadHydroModel (external)
Determines which set of equations to use within the solver. Default: 1.
1  - chemistry-dependent model, with case-B hydrogen II recombination
coefficient.
4  - chemistry-dependent model, with case-A hydrogen II recombination
coefficient, but assumes an isothermal gas energy.
10 - no chemistry, instead uses a model of local thermodynamic
equilibrium to couple radiation to gas energy.

RadHydroMaxDt (external)
maximum time step to use in the FLD solver. Default: 1e20 (no limit).
RadHydroMinDt (external)
minimum time step to use in the FLD solver. Default: 0.0 (no limit).
RadHydroInitDt (external)
initial time step to use in the FLD solver. Default: 1e20 (uses hydro time step).
RadHydroMaxSubcycles (external)
desired number of FLD time steps per hydrodynamics time step (must be greater than or equal to 1). This is only recommended if the FLD solver is performing chemistry and heating internally, since it will only synchronize with the ionization state at each hydrodynamic time step. When using Enzo’s chemistry and cooling solvers this parameter should be set to 1 to avoid overly decoupling radiation and chemistry. Default: 1.0.
RadHydroMaxChemSubcycles (external)
desired number of chemistry time steps per FLD time step. This only applies if the FLD solver is performing chemistry and heating internally, instead of using Enzo’s built-in routines for this task. Default: 1.0.
RadHydroDtNorm (external)
type of p-norm to use in estimating time-accuracy for predicting next time step. Default: 2.0.
0  - use the max-norm.
>0 - use the specified p-norm.
<0 - illegal.

RadHydroDtGrowth (external)
Maximum growth factor in the FLD time step between successive iterations. Default: 1.1 (10% growth).
RadHydroDtRadFac (external)
Desired time accuracy tolerance for the radiation field. Default: 1e20 (unused).
RadHydroDtGasFac (external)
Desired time accuracy tolerance for the gas energy field. Only used if the FLD solver is performing heating internally. Default: 1e20 (unused).
RadHydroDtChemFac (external)
Desired time accuracy tolerance for the hydrogen I number density. Only used if the FLD solver is performing chemistry internally. Default: 1e20 (unused).
RadiationScaling (external)
Scaling factor for the radiation field, in case standard non-dimensionalization fails. Default: 1.0.
EnergyCorrectionScaling (external)
Scaling factor for the gas energy correction, in case standard non-dimensionalization fails. Default: 1.0.
ChemistryScaling (external)
Scaling factor for the hydrogen I number density, in case standard non-dimensionalization fails. Default: 1.0.
AutomaticScaling (external)
Enables an heuristic approach in the FLD solver to update the above scaling factors internally. Works well for reioniztaion calculations, but is not recommended for problems in which the optimal unit scaling factor is known a-priori. Default: 1.0.
RadiationBoundaryX0Faces (external)

Boundary condition types to use on the x0 faces of the radiation field. Default: [0 0].

0 - Periodic.
1 - Dirichlet.
2 - Neumann.

RadiationBoundaryX1Faces (external)
Boundary condition types to use on the x1 faces of the radiation field. Default: [0 0].
RadiationBoundaryX2Faces (external)
Boundary condition types to use on the x2 faces of the radiation field. Default: [0 0].
RadHydroTheta (external)
Time-discretization parameter to use, 0 gives explicit Euler, 1 gives implicit Euler, 0.5 gives trapezoidal. Default: 1.0.
RadHydroKrylovMethod (external)

Desired outer linear solver algorithm to use. Default: 1.

0 - Preconditioned Conjugate Gradient (PCG)
1 - Stabilized Bi-Conjugate Gradient (BiCGStab)
2 - Generalized Minimum Residual (GMRES)

RadHydroSolTolerance (external)
Desired accuracy for solution to satisfy linear residual (measured in the 2-norm). Default: 1e-8.
RadHydroMaxMGIters (external)
Allowed number of iterations for the inner linear solver (geometric multigrid). Default: 50.
RadHydroMGRelaxType (external)

Relaxation method used by the multigrid solver. Default: 1.

0 - Jacobi
1 - Weighted Jacobi
2 - Red/Black Gauss-Seidel (symmetric)
3 - Red/Black Gauss-Seidel (non-symmetric)

RadHydroMGPreRelax (external)
Number of pre-relaxation sweeps used by the multigrid solver. Default: 1.
RadHydroMGPostRelax (external)
Number of post-relaxation sweeps used by the multigrid solver. Default: 1.
EnergyOpacityC0, EnergyOpacityC1, EnergyOpacityC2 (external)
Parameters used in defining the energy-mean opacity used with RadHydroModel 10. Default: [1 1 0].

## Cosmology Parameters¶

ComovingCoordinates (external)
Flag (1 - on, 0 - off) that determines if comoving coordinates are used or not. In practice this turns on or off the entire cosmology machinery. Default: 0
CosmologyFinalRedshift (external)
This parameter specifies the redshift when the calculation will halt. Default: 0.0
CosmologyOmegaMatterNow (external)
This is the contribution of all non-relativistic matter (including HDM) to the energy density at the current epoch (z=0), relative to the value required to marginally close the universe. It includes dark and baryonic matter. Default: 0.279
CosmologyOmegaLambdaNow (external)
This is the contribution of the cosmological constant to the energy density at the current epoch, in the same units as above. Default: 0.721
CosmologyOmegaRadiationNow (external)
This is the contribution of all relativistic matter to the energy density at the current epoch (z=0), in the same units as above. Default: 0.0.
CosmologyHubbleConstantNow (external)
The Hubble constant at z=0, in units of 100 km/s/Mpc. Default: 0.701
CosmologyComovingBoxSize (external)
The size of the volume to be simulated in Mpc/h (at z=0). Default: 64.0
CosmologyInitialRedshift (external)
The redshift for which the initial conditions are to be generated. Default: 20.0
CosmologyMaxExpansionRate (external)
This float controls the timestep so that cosmological terms are accurate followed. The timestep is constrained so that the relative change in the expansion factor in a step is less than this value. Default: 0.01
CosmologyTableNumberOfBins (external)
Conversions between time and redshift are computed by interpolating from a numerically integrated table of log(scale factor) vs. time. This parameter sets the number of bins in the table. Default: 1000.
CosmologyTableLogaInitial (external)
This sets the lower bound of the table used to convert between time and redshift. This is log10 of the lowest value of the scale factor. This value will be automatically adjusted if CosmologyInitialRedshift is set to an earlier time. Default: -6.0, (i.e., z = 999,999.)
CosmologyTableLogaFinal (external)
This sets the upper bound of the table used to convert between time and redshift. This is log10 of the highest value of the scale factor. This value will be automatically adjusted if CosmologyFinalRedshift is set to a later time. Default: 0.0, (i.e., z = 0.)
CosmologyCurrentRedshift (information only)
This is not strictly speaking a parameter since it is never interpreted and is only meant to provide information to the user. Default: n/a

## Massive Black Hole Physics Parameters¶

Following parameters are for the accretion and feedback from the massive black hole particle (PARTICLE_TYPE_MBH). Details are described in Kim, Wise, Alvarez, and Abel (2011).

### Accretion Physics¶

MBHAccretion (external)
Set to 1 to turn on accretion based on the Eddington-limited spherical Bondi-Hoyle formula (Bondi 1952). Set to 2 to turn on accretion based on the Bondi-Hoyle formula but with fixed temperature defined below. Set to 3 to turn on accretion with a fixed rate defined below. Set to 4 to to turn on accretion based on the Eddington-limited spherical Bondi-Hoyle formula, but without v_rel in the denominator. Set to 5 to turn on accretion based on Krumholz et al.(2006) which takes vorticity into account. Set to 6 to turn on alpha disk formalism based on DeBuhr et al.(2010). 7 and 8 are still failed experiment. Add 10 to each of these options (i.e. 11, 12, 13, 14) to ignore the Eddington limit. See Star_CalculateMassAccretion.C. Default: 0 (FALSE)
MBHAccretionRadius (external)
This is the radius (in pc) of a gas sphere from which the accreting mass is subtracted out at every timestep. Instead, you may want to try set this parameter to -1, in which case an approximate Bondi radius is calculated and used (from DEFAULT_MU and MBHAccretionFixedTemperature). If set to -N, it will use N*(Bondi radius). See CalculateSubtractionParameters.C. Default: 50.0
MBHAccretingMassRatio (external)
There are three different scenarios you can utilize this parameter. (1) In principle this parameter is a nondimensional factor multiplied to the Bondi-Hoyle accretion rate; so 1.0 should give the plain Bondi rate. (2) However, if the Bondi radius is resolved around the MBH, the local density used to calculate Mdot can be higher than what was supposed to be used (density at the Bondi radius!), resulting in the overestimation of Mdot. 0.0 < MBHAccretingMassRatio < 1.0 can be used to fix this. (3) Or, one might try using the density profile of R-1.5 to estimate the density at the Bondi radius, which is utilized when MBHAccretingMassRatio is set to -1. See Star_CalculateMassAccretion.C. Default: 1.0
MBHAccretionFixedTemperature (external)
This parameter (in K) is used when MBHAccretion = 2. A fixed gas temperature that goes into the Bondi-Hoyle accretion rate estimation formula. Default: 3e5
MBHAccretionFixedRate (external)
This parameter (in Msun/yr) is used when MBHAccretion = 3. Default: 1e-3
MBHTurnOffStarFormation (external)
Set to 1 to turn off star formation (only for StarParicleCreation method 7) in the cells where MBH particles reside. Default: 0 (FALSE)
MBHCombineRadius (external)
The distance (in pc) between two MBH particles in which two energetically-bound MBH particles merge to form one particle. Default: 50.0
MBHMinDynamicalTime (external)
Minimum dynamical time (in yr) for a MBH particle. Default: 1e7
MBHMinimumMass (external)
Minimum mass (in Msun) for a MBH particle. Default: 1e3

### Feedback Physics¶

MBHFeedback (external)
Set to 1 to turn on thermal feedback of MBH particles (MBH_THERMAL - not fully tested). Set to 2 to turn on mechanical feedback of MBH particles (MBH_JETS, bipolar jets along the total angular momentum of gas accreted onto the MBH particle so far). Set to 3 to turn on another version of mechanical feedback of MBH particles (MBH_JETS, always directed along z-axis). Set to 4 to turn on experimental version of mechanical feedback (MBH_JETS, bipolar jets along the total angular momentum of gas accreted onto the MBH particle so far + 10 degree random noise). Set to 5 to turn on experimental version of mechanical feedback (MBH_JETS, launched at random direction). Note that, even when this parameter is set to 0, MBH particles still can be radiation sources if RadiativeTransfer is on. See Grid_AddFeedbackSphere.C. Default: 0 (FALSE)
RadiativeTransfer = 0 & MBHFeedback = 0 : no feedback at all
RadiativeTransfer = 0 & MBHFeedback = 1 : purely thermal feedback
RadiativeTransfer = 0 & MBHFeedback = 2 : purely mechanical feedback
RadiativeTransfer = 1 & MBHFeedback = 0 : purely radiative feedback
RadiativeTransfer = 1 & MBHFeedback = 2 : radiative and
mechanical feedback combined (one has to change the following
MBHFeedbackRadiativeEfficiency parameter accordingly, say from 0.1
to 0.05, to keep the same total energy across different modes of
feedback)

MBHFeedbackRadiativeEfficiency (external)
The radiative efficiency of a black hole. 10% is the widely accepted value for the conversion rate from the rest-mass energy of the accreting material to the feedback energy, at the innermost stable orbit of a non-spinning Schwarzschild black hole (Shakura & Sunyaev 1973, Booth & Schaye 2009). Default: 0.1
MBHFeedbackEnergyCoupling (external)
The fraction of feedback energy that is thermodynamically (for MBH_THERMAL) or mechanically (for MBH_JETS) coupled to the gas. 0.05 is widely used for thermal feedback (Springel et al. 2005, Di Matteo et al. 2005), whereas 0.0001 or less is recommended for mechanical feedback depending on the resolution of the simulation (Ciotti et al. 2009). Default: 0.05
MBHFeedbackMassEjectionFraction (external)
The fraction of accreting mass that is returning to the gas phase. For either MBH_THERMAL or MBH_JETS. Default: 0.1
MBHFeedbackMetalYield (external)
The mass fraction of metal in the ejected mass. Default: 0.02
MBHFeedbackThermalRadius (external)
The radius (in pc) of a sphere in which the energy from MBH_THERMAL feedback is deposited. If set to a negative value, the radius of a sphere gets bigger in a way that the sphere encloses the constant mass (= 4/3*pi*(-MBHFeedbackThermalRadius)3 Msun). The latter is at the moment very experimental; see Star_FindFeedbackSphere.C. Default: 50.0
MBHFeedbackJetsThresholdMass (external)
The bipolar jets by MBH_JETS feedback are injected every time the accumulated ejecta mass surpasses MBHFeedbackJetsThresholdMass (in Msun). Although continuously injecting jets into the gas cells might sound great, unless the gas cells around the MBH are resolved down to Mdot, the jets make little or no dynamical impact on the surrounding gas. By imposing MBHFeedbackJetsThresholdMass, the jets from MBH particles are rendered intermittent, yet dynamically important. Default: 10.0
MBHParticleIO (external)
Set to 1 to print out basic information about MBH particles. Will be automatically turned on if MBHFeedback is set to 2 or 3. Default: 0 (FALSE)
MBHParticleIOFilename (external)
The name of the file used for the parameter above. Default: mbh_particle_io.dat

## Shock Finding Parameters¶

For details on shock finding in Enzo see Shock Finding.

ShockMethod (external)
This parameter controls the use and type of shock finding. Default: 0
0 - Off
1 - Temperature Dimensionally Unsplit Jumps
2 - Temperature Dimensionally Split Jumps
3 - Velocity Dimensionally Unsplit Jumps
4 - Velocity Dimensionally Split Jumps

ShockTemperatureFloor (external)
When calculating the mach number using temperature jumps, set the temperature floor in the calculation to this value.
StorePreShockFields (external)
Optionally store the Pre-shock Density and Temperature during data output.
FindShocksOnlyOnOutput (external)
0: Finds shocks during Evolve Level and just before writing out data. 1: Only find shocks just before writing out data. 2: Only find shocks during EvolveLevel. Default: 0

## Cosmic Ray Two-Fluid Model Parameters¶

For details on the cosmic ray solver in Enzo see Cosmic Ray Two-Fluid Model.

CRModel (external)

This parameter turns on the model. Default: 0

1. Off
2. On
CRgamma
For CR equation of state. Default: 4.0/3.0 (relativistic, adiabatic gas)
CRDiffusion (external)

Switches on diffusion of the cosmic ray energy density. Default: 0

1. Off
2. On with constant coefficient (CRkappa)
CRkappa (external)
Cosmic ray diffusion coefficient in CGS units (cm^2/s), Default: 0.0. For MW-like galaxies: 1E28.
CRCourantSafetyNumber (external)
Multiplies CR diffusion timestep, for stability should be <= 0.5. Default: 0.5
CRFeedback (external)
Specify fraction of star formation feedback energy should be diverted into the cosmic ray energy density. implemented ONLY for star_maker3 (feedback method 2). Default: 0.0
CRdensFloor (external)
Floor in gas density, can be imposed, for speed purposes (default 0.0 = off). Any value larger than 0.0 is on with that value as the floor in code units.

## Conduction¶

Isotropic and anisotropic thermal conduction are implemented using the method of Parrish and Stone: namely, using an explicit, forward time-centered algorithm. In the anisotropic conduction, heat can only conduct along magnetic field lines. One can turn on the two types of conduction independently, since there are situations where one might want to use both. The Spitzer fraction can be also set independently for the isotropic and anisotropic conduction. Running a cosmological simulation with conduction on can be tricky as the timesteps can become very short. It is recommended that you look carefully at all the available conduction parameters. Additionally, if you intend to run with star particles, it is highly recommended that you set the parameter, StarMakerTimeIndependentFormation. See the description in Star Formation and Feedback Parameters for more information.

IsotropicConduction (external)
Turns on isotropic thermal conduction using Spitzer conduction. Default: 0 (FALSE)
AnisotropicConduction (external)
Turns on anisotropic thermal conduction using Spitzer conduction. Can only be used if MHD is turned on (HydroMethod = 4). Default: 0 (FALSE)
IsotropicConductionSpitzerFraction (external)
Prefactor that goes in front of the isotropic Spitzer conduction coefficient. Should be a value between 0 and 1. Default: 1.0
AnisotropicConductionSpitzerFraction (external)
Prefactor that goes in front of the anisotropic Spitzer conduction coefficient. Should be a value between 0 and 1. Default: 1.0
ConductionCourantSafetyNumber (external)
This is a prefactor that controls the stability of the conduction algorithm. In its current explicit formulation, it must be set to a value of 0.5 or less. Default: 0.5
SpeedOfLightTimeStepLimit (external)
When used, this sets a floor for the conduction timestep to be the local light crossing time (dx / c). This prevents the conduction machinery from prescribing extremely small timesteps. While this can technically violate the conduction stability criterion, testing has shown that this does not result in notable differences. (1 - ON; 0 - OFF) Default: 0 (OFF).
ConductionDynamicRebuildHierarchy (external)
Using conduction can often result in the code taking extremely short timesteps. Since the hierarchy is rebuilt each timestep, this can exacerbate memory fragmentation issues and slow the simulation. In the case where the conduction timestep is the limiter, the hierarchy should not need to be rebuilt every timestep since conduction mostly does not alter the fields which control refinement. When this option is used, the timestep calculation is carried out as usual, but the hierarchy is only rebuilt on a timescale that is calculated neglecting the conduction timestep. This results in a decent speedup and reduced memory fragmentation when running with conduction. (1 - ON; 0 - OFF) Default: 0 (OFF).
ConductionDynamicRebuildMinLevel (external)
The minimum level on which the dynamic hierarcy rebuild is performed. Default: 0.

## Subgrid-scale (SGS) turbulence model¶

The following parameter allow the use of an SGS turbulence model in Enzo, see test problem run/MHD/3D/StochasticForcing/StochasticForcing.enzo.

It is recommended to not arbitrarily mix model terms, but either stick to one model family (nonlinear, dissipative, or scale-similarity) or conduct additional a priori test first.

Best fit model coefficients based on a priori testing of compressible MHD turbulence for a wide range of sonic Mach numbers (0.2 to 20) can be found in Table II in Grete et al. (2016) Physics of Plasmas 23 062317, where all models are presented in more detail.

Overall, the nonlinear model (effectively parameter free) with an explicit 3-point stencil showed the best performance in decaying MHD test problem, see Grete et al. (2017) Phys. Rev. E. 95 033206.

UseSGSModel (external)
This parameter generally turns the SGS machinery on (even though no SGS term is added by default as every term needs a coefficient, see below). 1: Turn on. Default: 0

### Explicit filtering¶

All SGS models rely on the notion that they are calculated based on filtered/resolved quantities. The spatial discretization itself acts as one filter. However, in shock-capturing schemes it is questionable how “resolved” quantities are at the grid-scale. The following three variables enable the explicit filtering of the grid-scale quantites as they are used in the SGS terms.

See Table 1 in Grete et al. (2017) Phys. Rev. E. 95 033206 for coefficients of a discrete box filter. The recommended values correspond to a discrete representation of a box filter on a 3-point stencil.

SGSFilterWidth (external)
Width (in units of cell widths) of the discrete filter. Default: 0; Recommended: 2.711;
SGSFilterStencil (external)
Discrete width of filter stencil in numbers of cells. Default: 0; Recommended: 3; Maximum: 7;
SGSFilterWeights (external)
Symmetic filter weights that are used in the stencil. List of four floats. First number corresponds to weight of central point X_i, second number corresponds to weight of points X_i+1 and X_i-1, and so on. Default: 0. 0. 0. 0.; Recommended: 0.40150 0.29925 0.00000 0.0;

### Nonlinear model¶

SGScoeffNLu (external)
Coefficient for nonlinear Reynolds stress model. Default: 0; Recommended: 1;
SGScoeffNLb (external)
Coefficient for nonlinear Maxwell stress (only MHD). Default: 0; Recommended: 1;
SGScoeffNLemfCompr (external)
Coefficient for nonlinear compressive EMF model (only MHD). Default: 0; Recommended: 1;

### Dissipative model¶

SGScoeffEVStarEnS2Star (external)
Coefficient for traceless eddy-viscosity Reynolds stress model (scaled by realizability condition in the kinetic SGS energy). Default: 0; Recommended: 0.01;
SGScoeffEnS2StarTrace (external)
Coefficient for the trace of the eddy-viscosity Reynolds stress model, i.e., the kinetic SGS energy (derived from realizability condition). Default: 0; Recommended: 0.08;
SGScoeffERS2M2Star (external)
Coefficient for eddy-resistivity EMF model (only MHD; scaled by realizable SGS energies) Default: 0; Recommended: 0.012;
SGScoeffERS2J2 (external)
Coefficient for eddy-resistivity EMF model (only MHD; scaled by Smagorinsky SGS energies) Default: 0;

### Scale-similarity model¶

SGScoeffSSu (external)
Coefficient for scale-similarity Reynolds stress model. Default: 0; Recommended: 0.67;
SGScoeffSSb (external)
Coefficient for scale-similarity Maxwell stress (only MHD). Default: 0; Recommended: 0.9;
SGScoeffNLemfCompr (external)
Coefficient for scale-similarity EMF model (only MHD). Default: 0; Recommended: 0.89;

## Fuzzy Dark matter model¶

QuantumPressure (external)
Flag to turn on quantum pressure machinery (see Li, Hui & Bryan 2019) Default: 0;
FDMMass (external)
If QuantumPressure is used, this indicates the mass of the FDM particle in units of 1e-22 eV. Default: 1;

## Other Parameters¶

### Other External Parameters¶

huge_number (external)
The largest reasonable number. Rarely used. Default: 1e+20
tiny_number (external)

A number which is smaller than all physically reasonable numbers. Used to prevent divergences and divide-by-zero in C++ functions. Modify with caution! Default: 1e-20.

An independent analog, tiny, defined in fortran.def, does the same job for a large family of FORTRAN routines. Modification of tiny must be done with caution and currently requires recompiling the code, since tiny is not a runtime parameter.

TimeActionParameter[#]
Reserved for future use.
TimeActionRedshift[#]
Reserved for future use.
TimeActionTime[#]
Reserved for future use.
TimeActionType[#]
Reserved for future use.
StopSteps
Reserved for future use
CoolDataf0to3
Reserved for future use
StageInput
Reserved for future use
LocalPath
Reserved for future use
GlobalPath
Reserved for future use

## Inline Analysis¶

### Inline Halo Finding¶

Enzo can find dark matter (sub)halos on the fly with a friends-of-friends (FOF) halo finder and a subfind method, originally written by Volker Springel. All output files will be written in the directory FOF/.

InlineHaloFinder (external)
Set to 1 to turn on the inline halo finder. Default: 0.
HaloFinderSubfind (external)
Set to 1 to find subhalos inside each dark matter halo found in the friends-of-friends method. Default: 0.
HaloFinderOutputParticleList (external)
Set to 1 to output a list of particle positions and IDs for each (sub)halo. Written in HDF5. Default: 0.
HaloFinderMinimumSize (external)
Minimum number of particles to be considered a halo. Default: 50.
HaloFinderLinkingLength (external)
Linking length of particles when finding FOF groups. In units of cell width of the finest static grid, e.g. unigrid -> root cell width. Default: 0.1.
HaloFinderCycleSkip (external)
Find halos every Nth top-level timestep, where N is this parameter. Not used if set to 0. Default: 3.
HaloFinderTimestep (external)
Find halos every dt = (this parameter). Only evaluated at each top-level timestep. Not used if negative. Default: -99999.0
HaloFinderRunAfterOutput (external)
When turned on, the inline halo finder is run after an output is written. Default: 0
HaloFinderLastTime (internal)
Last time of a halo find. Default: 0.

### Inline Python¶

PythonTopGridSkip (external)
How many top grid cycles should we skip between calling python at the top of the hierarchy? Only works with python-yes in compile settings.
PythonSubcycleSkip (external)
How many subgrid cycles should we skip between calling python at the bottom of the hierarchy?
PythonReloadScript (external)
Should “user_script.py” be reloaded in between Python calls?
NumberOfPythonCalls (internal)
Internal parameter tracked by Enzo
NumberOfPythonTopGridCalls (internal)
Internal parameter tracked by Enzo
NumberOfPythonSubcycleCalls (internal)
Internal parameter tracked by Enzo

### Other Internal Parameters¶

TimeLastDataDump (internal)
The code time at which the last time-based output occurred.
TimeLastInterpolatedDataDump (internal)
The code time at which the last interpolated data dump occurred.
CycleLastDataDump (internal)
The last cycle on which a cycle dump was made
SubcycleLastDataDump (internal)
The last cycle on which a subcycle dump was made
TimeLastMovieDump (internal)
The code time at which the last movie dump occurred.
TimeLastTracerParticleDump (internal)
The code time at which the last tracer particle dump occurred.
TimeLastRestartDump
Reserved for future use.
TimeLastHistoryDump
Reserved for future use.
CycleLastRestartDump
Reserved for future use.
CycleLastHistoryDump
Reserved for future use.
InitialCPUTime
Reserved for future use.
InitialCycleNumber (internal)
The current cycle
SubcycleNumber (internal)
The current subcycle
DataDumpNumber (internal)
The identification number of the next output file (the 0000 part of the output name). This is used and incremented by both the cycle based and time based outputs. Default: 0
MovieDumpNumber (internal)
The identification number of the next movie output file. Default: 0
TracerParticleDumpNumber (internal)
The identification number of the next tracer particle output file. Default: 0
RestartDumpNumber
Reserved for future use.
HistoryDumpNumber
Reserved for future use.
DataLabel[#] (internal)
These are printed out into the restart dump parameter file. One Label is produced per baryon field with the name of that baryon field. The same labels are used to name data sets in HDF files.
DataUnits[#]
Reserved for future use.
VersionNumber (internal)
Sets the version number of the code which is written out to restart dumps.

## Problem Type Parameters¶

ProblemType (external)
This integer specifies the type of problem to be run. Its value causes the correct problem initializer to be called to set up the grid, and also may trigger certain boundary conditions or other problem-dependent routines to be called. The possible values are listed below. Default: none.

For other problem-specific parameters follow the links below. The problems marked with “hydro_rk” originate from the MUSCL solver package in the enzo installation directory src/enzo/hydro_rk. For the 4xx radiation hydrodynamics problem types, see the user guides in the installation directory doc/implicit_fld and doc/split_fld.

Problem Type Description and Parameter List
1 Shock Tube (1: unigrid and AMR)
2 Wave Pool (2)
3 Shock Pool (3: unigrid 2D, AMR 2D and unigrid 3D)
4 Double Mach Reflection (4)
5 Shock in a Box (5)
6 Implosion (6)
7 Sedov Blast (7)
8 Kelvin-Helmholtz Instability (8)
9 2D/3D Noh Problem (9)
10 Rotating Cylinder (10)
12 Free Expansion (12)
14 Rotating Sphere (14)
20 Zeldovich Pancake (20)
21 Pressureless Collapse (21)
23 Test Gravity (23)
24 Spherical Infall (24)
25 Test Gravity: Sphere (25)
26 Gravity Equilibrium Test (26)
27 Collapse Test (27)
28 Test Gravity Motion (28)
29 Test Orbit (29)
30 Cosmology Simulation (30)
31 Isolated Galaxy Evolution (31)
35 Shearing Box Simulation (35)
36 Shearing Box 2D Simulation
37 Stratifeid Shearing Box Simulation
40 Supernova Restart Simulation (40)
50 Photon Test (50)
51 Photon Test Restart
59 Turbulence Simulation with Stochastic Forcing (59)
60 Turbulence Simulation (60)
61 Protostellar Collapse (61)
62 Cooling Test (62)
63 One Zone Free Fall Test
70 Conduction Test with Hydro Off
71 Conduction Test with Hydro On
72 Conduction Bubble Test
73 Conduction Cloud Test
80 Explosion in a Stratified Medium Test
101 3D Collapse Test (101)
102 1D Spherical Collapse Test (102)
106 Hydro and MHD Turbulence Simulation (106)
107 Put Sink from Restart (107)
108 Cluster Cooling Flow (108)
190 Light Boson Initialize
191 FDM Collapse
200 1D MHD Test (200)
201 2D MHD Test (201)
202 3D MHD Collapse Test (202)
203 MHD Turbulent Collapse Test (203)
204 3D MHD Test
207 Galaxy Disk (207)
208 AGN Disk (207)
209 MHD 1D Waves
210 MHD Decaying Random Magnetic Fields
250 CR Shock Tube (250: unigrid and AMR)
300 Poisson Solver Test (300)
400 Radiation-Hydrodynamics Test 1 - Constant Fields (400)
401 Radiation-Hydrodynamics Test 2 - Streams (401)
402 Radiation-Hydrodynamics Test 3 - Pulse (402)
403 Radiation-Hydrodynamics Test 4 - Grey Marshak Test (403)
410/411 Radiation-Hydrodynamics Tests 10 and 11 - I-Front Tests (410/411)
412 Radiation-Hydrodynamics Test 12 - HI ionization of a clump (412)
413 Radiation-Hydrodynamics Test 13 - HI ionization of a steep region (413)
414/415 Radiation-Hydrodynamics Tests 14/15 - Cosmological HI ionization (414/415)
450-452 Free-streaming radiation tests (to be removed)

### Shock Tube (1: unigrid and AMR)¶

Riemann problem or arbitrary discontinuity breakup problem. The discontinuity initially separates two arbitrary constant states: Left and Right. Default values correspond to the so called Sod Shock Tube setup (test 1.1). A table below contains a series of recommended 1D tests for hydrodynamic method, specifically designed to test the performance of the Riemann solver, the treatment of shock waves, contact discontinuities, and rarefaction waves in a variety of situations (Toro 1999, p. 129).

It is also possible to set up a second discontinuity, creating three initial regions, rather than the two regions of the original Sod Shock Tube.

Test  LeftDensity LeftVelocity LeftPressure RightDensity RightVelocity RightPressure
1.1   1.0         0.0          1.0          0.125        0.0           0.1
1.2   1.0         -2.0         0.4          1.0          2.0           0.4
1.3   1.0         0.0          1000.0       1.0          0.0           0.01
1.4   1.0         0.0          0.01         1.0          0.0           100.0
1.5   5.99924     19.5975      460.894      5.99242      -6.19633      46.0950

HydroShockTubesInitialDiscontinuity (external)
The position of the initial discontinuity. Default: 0.5
HydroShockTubesSecondDiscontinuity (external)
The position of the second discontinuity, if a second discontinuity is desired. Default: FLOAT_UNDEFINED, i.e. no second discontinuity.
HydroShockTubesLeftDensity, HydroShockTubesRightDensity, HydroShockTubesCenterDensity (external)
The initial gas density to the left and right of the discontinuity, and between the discontinuities if a second discontinuity has been specified with HydroShockTubesSecondDiscontinuity. Default: 1.0 for each value.
HydroShockTubesLeftPressure, HydroShockTubesRightPressure, HydroShockTubesCenterPressure (external)
The initial gas density to the left and right of the discontinuity, and between the discontinuities if a second discontinuity has been specified with HydroShockTubesSecondDiscontinuity. Default: 1.0 for each of the left, right, and center regions.
HydroShockTubesLeftVelocityX, HydroShockTubesLeftVelocityY, HydroShockTubesLeftVelocityZ (external)
The initial gas velocity, in the x-, y-, and z-directions to the left of the discontinuity. Default: 0.0 for all directions.
HydroShockTubesRightVelocityX, HydroShockTubesRightVelocityY, HydroShockTubesRightVelocityZ (external)
The initial gas velocity, in the x-, y-, and z-directions to the right of the discontinuity. Default: 0.0 for all directions.
HydroShockTubesCenterVelocityX, HydroShockTubesCenterVelocityY, HydroShockTubesCenterVelocityZ (external)
The initial gas velocity, in the x-, y-, and z-directions between the discontinuities, used if a second discontinuity has been specified with HydroShockTubesSecondDiscontinuity. Default: 1.0 for all directions.

### Wave Pool (2)¶

Wave Pool sets up a simulation with a 1D sinusoidal wave entering from the left boundary. The initial active region is uniform and the wave is entered via inflow boundary conditions.
WavePoolAmplitude (external)
The amplitude of the wave. Default: 0.01 - a linear wave.
WavePoolAngle (external)
Direction of wave propagation with respect to x-axis. Default: 0.0
WavePoolDensity (external)
Uniform gas density in the pool. Default: 1.0
WavePoolNumberOfWaves (external)
The test initialization will work for one wave only. Default: 1
WavePoolPressure (external)
Uniform gas pressure in the pool. Default: 1.0
WavePoolSubgridLeft, WavePoolSubgridRight (external)
Start and end positions of the subgrid. Default: 0.0 and 0.0 (no subgrids)
WavePoolVelocity1(2,3) (external)
x-,y-, and z-velocities. Default: 0.0 (for all)
WavePoolWavelength (external)
The wavelength. Default: 0.1 (one-tenth of the box)

### Shock Pool (3: unigrid 2D, AMR 2D and unigrid 3D)¶

The Shock Pool test sets up a system which introduces a shock from the left boundary. The initial active region is uniform, and the shock wave enters via inflow boundary conditions. 2D and 3D versions available. (D. Mihalas & B.W. Mihalas, Foundations of Radiation Hydrodynamics, 1984, p. 236, eq. 56-40.)
ShockPoolAngle (external)
Direction of the shock wave propagation with respect to x-axis. Default: 0.0
ShockPoolDensity (external)
Uniform gas density in the preshock region. Default: 1.0
ShockPoolPressure (external)
Uniform gas pressure in the preshock region. Default: 1.0
ShockPoolMachNumber (external)
The ratio of the shock velocity and the preshock sound speed. Default: 2.0
ShockPoolSubgridLeft, ShockPoolSubgridRight (external)
Start and end positions of the subgrid. Default: 0.0 and 0.0 (no subgrids)
ShockPoolVelocity1(2,3) (external)
Preshock gas velocity (the Mach number definition above assumes a zero velocity in the laboratory reference frame. Default: 0.0 (for all components)

### Double Mach Reflection (4)¶

A test for double Mach reflection of a strong shock (Woodward & Colella 1984). Most of the parameters are “hardwired”: d0 = 8.0, e0 = 291.25, u0 = 8.25*sqrt(3.0)/2.0, v0 = -8.25*0.5, w0 = 0.0
DoubleMachSubgridLeft (external)
Start position of the subgrid. Default: 0.0
DoubleMachSubgridRight (external)
End positions of the subgrid. Default: 0.0

### Shock in a Box (5)¶

A stationary shock front in a static 3D subgrid (Anninos et al. 1994). Initialization is done as in the Shock Tube test.
ShockInABoxBoundary (external)
Position of the shock. Default: 0.5
ShockInABoxLeftDensity, ShockInABoxRightDensity (external)
Densities to the right and to the left of the shock front. Default: dL=1.0 and dR = dL*((Gamma+1)*m^2)/((Gamma-1)*m^2 + 2), where m=2.0 and speed=0.9*sqrt(Gamma*pL/dL)*m.
ShockInABoxLeftVelocity, ShockInABoxRightVelocity (external)
Velocities to the right and to the left of the shock front. Default: vL=shockspeed and vR=shockspeed-m*sqrt(Gamma*pL/dL)*(1-dL/dR), where m=2.0, shockspeed=0.9*sqrt(Gamma*pL/dL)*m.
ShockInABoxLeftPressure, ShockInABoxRightPressure (external)
Pressures to the Right and to the Left of the shock front. Default: pL=1.0 and pR=pL*(2.0*Gamma*m^2 - (Gamma-1))/(Gamma+1), where m=2.0.
ShockInABoxSubgridLeft, ShockInABoxSubgridRight (external)
Start and end positions of the subgrid. Default: 0.0 (for both)

### Implosion (6)¶

The implosion test sets up a converging shock problem in a square domain (x,y) in (0, 0.3)x(0, 0.3) with gas initially at rest. Initial pressure and density is 1 everywhere except for a triangular region (0.15,0)(0.15,0) where d=0.125 and p=0.14. Reflecting boundary conditions at all boundaries. Adiabatic index gamma=1.4.

If AMR is used, a hierarchy of subgrids (one per level) will be generated at start-up to properly resolve the initial discontinuity.

REFERENCE: Hui Li and Z. Li, JCP 153, 596, 1999.
Chang et al. JCP 160, 89, 1999.
ImplosionDensity (external)
Initial density. Default: 1.0
ImplosionPressure (external)
Initial pressure. Default: 1.0
ImplosionDimaondDensity (external)
Initial density within diamond. Default: 0.125
ImplosionDimaondPressure (external)
Initial pressure within diamond. Default: 0.14
ImplosionSubgridLeft, ImplosionSubgridRight (external)
Start and position of the subgrid. Default: 0.0 (for both)

### Sedov Blast (7)¶

Self-similar solution: L.I. Sedov (1946); see also: Sedov (1959), Similarity and Dimensional Methods in Mechanics, pp. 210, 219, 228; see also: Landau & Lifshitz, Fluid Dynamics, Sect. 99 “The Propagation of Strong Shock Waves” (1959). Experiments, terrestrial/numerical: Taylor (1941, 1949).
SedovBlastFullBox (external)
Full box or one quadrant. Default: 0
SedovBlastType (external)
2D. Default: 0
SedovBlastInitialTime (external)
Initial time. Default: 0
SedovBlastDensity (external)
Initial density. Default: 1.0
SedovBlastPressure (external)
Initial pressure. Default: 1e-5
SedovBlastInputEnergy (external)
Energy input into system. Default: 1.0
SedovBlastEnergyZones (external)
Default: 3.5
SedovBlastSubGridLeft, SedovBlastSubGridRight (external)
Start and end position of the subgrid. Default: 0.0 (for both)

### Kelvin-Helmholtz Instability (8)¶

This problem sets up a 2D box with periodic boundary conditions containing two fluids (inner fluid and outer fluid). The inner fluid has a positive velocity and the outer fluid has a negative velocity with a difference of KHVelocityJump. The two fluids typically have different densities. The result is the build up of KH instabilities along the interface between the two fluids.

Setting KHRamp to 0, creates the standard KH test problem where there is a discontinuous jump between the two fluids in x-velocity and density. Random perturbations in y-velocity are the seeds to the KH instability resulting in growth of multiple modes of the KHI.

Setting KHRamp to 1 modifies the ICs so that there is a smooth ramp connecting the two fluids in x-velocity and density of width KHRampWidth. A sinusoidal perturbation in y-velocity is the seed to the KH instability resulting in only growth of k=2 modes. These results converge in behavior as resolution is increased, whereas the standard ICs do not. The ramped ICs are based on Robertson, Kravtsov, Gnedin, Abel & Rudd 2010, but that work has a typo in the ramp equation, and this implementation matches Robertson’s actual ICs.

KHInnerDensity, KHOuterDensity (external)
Initial density. Default: 2.0 (inner) and 1.0 (outer)
KHInnerPressure, KHOuterPressure (external)
Initial pressure. Default: 2.5 (for both)
KHBulkVelocity (external)
The bulk velocity of both fluids relative to the grid. Default: 0.0
KHVelocityJump (external)
The difference in velocity between the outer fluid and the inner fluid. Inner fluid will have half this value and move to the right (positive), whereas outer fluid will have have this value and move to the left (negative). Total fluid velocities will combine this jump with KHBulkVelocity. Default: 1.0
KHPerturbationAmplitude (external)
Default: 0.1
KHRamp (external)
Whether to use ramped ICs or not. Default: 1
KHRampWidth (external)
The width in y-space of the transition ramp. Default: 0.05
KHRandomSeed (external)
The seed for the Mersennes random number generator. This is only used in the case of the KHRamp=0 ICs. By using the same seed from one run to the next, one can reproduce previous behavior with identical parameter files. Default: 123456789

### 2D/3D Noh Problem (9)¶

Liska & Wendroff, 2003, SIAM J. Sci. Comput. 25, 995, Section 4.5, Fig. 4.4.
NohProblemFullBox (external)
Default: 0
NohSubgridLeft, NohSubgridRight (external)
Start and end positon of the subgrid. Default: 0.0 (for both)

### Rotating Cylinder (10)¶

A test for the angular momentum conservation of a collapsing cylinder of gas in an AMR simulation. Written by Brian O’Shea (oshea@msu.edu).
RotatingCylinderOverdensity (external)
Density of the rotating cylinder with respect to the background. Default: 20.0
RotatingCylinderSubgridLeft, RotatingCylinderSubgridRight (external)
This pair of floating point numbers creates a subgrid region at the beginning of the simulation that will be refined to MaximumRefinementLevel. It should probably encompass the whole cylinder. Positions are in units of the box, and it always creates a cube. No default value (meaning off).
RotatingCylinderLambda (external)
Angular momentum of the cylinder as a dimensionless quantity. This is identical to the angular momentum parameter lambda that is commonly used to describe cosmological halos. A value of 0.0 is non-rotating, and 1.0 means that the gas is already approximately rotating at the Keplerian value. Default: 0.05
RotatingCylinderTotalEnergy (external)
Sets the default gas energy of the ambient medium, in Enzo internal units. Default: 1.0
RotatingCylinderRadius (external)
Radius of the rotating cylinder in units of the box size. Note that the height of the cylinder is equal to the diameter. Default: 0.3
RotatingCylinderCenterPosition (external)
Position of the center of the cylinder as a vector of floats. Default: (0.5, 0.5, 0.5)

This is a test problem similar to the Sedov test problem documented elsewhere, but with radiative cooling turned on (and the ability to use MultiSpecies and all other forms of cooling). The main difference is that there are quite a few extras thrown in, including the ability to initialize with random density fluctuations outside of the explosion region, use a Sedov blast wave instead of just thermal energy, and some other goodies (as documented below).
RadiatingShockInnerDensity (external)
Density inside the energy deposition area (Enzo internal units). Default: 1.0
RadiatingShockOuterDensity (external)
Density outside the energy deposition area (Enzo internal units). Default: 1.0
RadiatingShockPressure (external)
Pressure outside the energy deposition area (Enzo internal units). Default: 1.0e-5
RadiatingShockEnergy (external)
Total energy deposited (in units of 1e51 ergs). Default: 1.0
RadiatingShockSubgridLeft, RadiatingShockSubgridRight (external)
Pair of floats that defines the edges of the region where the initial conditions are refined to MaximumRefinementLevel. No default value.
RadiatingShockUseDensityFluctuation (external)
Initialize external medium with random density fluctuations. Default: 0
RadiatingShockRandomSeed (external)
Seed for random number geneator (currently using Mersenne Twister). Default: 123456789
RadiatingShockDensityFluctuationLevel (external)
Maximum fractional fluctuation in the density level. Default: 0.1
RadiatingShockInitializeWithKE (external)
Initializes the simulation with some initial kinetic energy if turned on (0 - off, 1 - on). Whether this is a simple sawtooth or a Sedov profile is controlled by the parameter RadiatingShockUseSedovProfile. Default: 0
RadiatingShockUseSedovProfile (external)
If set to 1, initializes simulation with a Sedov blast wave profile (thermal and kinetic energy components). If this is set to 1, it overrides all other kinetic energy-related parameters. Default: 0
RadiatingShockSedovBlastRadius (external)
Maximum radius of the Sedov blast, in units of the box size. Default: 0.05
RadiatingShockKineticEnergyFraction (external)
Fraction of the total supernova energy that is deposited as kinetic energy. This only is used if RadiatingShockInitializeWithKE is set to 1. Default: 0.0
RadiatingShockCenterPosition (external)
Vector of floats that defines the center of the explosion. Default: (0.5, 0.5, 0.5)
RadiatingShockSpreadOverNumZones (external)
Number of cells that the shock is spread over. This corresponds to a radius of approximately N * dx, where N is the number of cells and dx is the resolution of the highest level of refinement. This does not have to be an integer value. Default: 3.5

### Free Expansion (12)¶

This test sets up a blast wave in the free expansion stage. There is only kinetic energy in the sphere with the radial velocity proportional to radius. If let evolve for long enough, the problem should turn into a Sedov-Taylor blast wave.

FreeExpansionFullBox (external)
Set to 0 to have the blast wave start at the origin with reflecting boundaries. Set to 1 to center the problem at the domain center with periodic boundaries. Default: 0
FreeExpansionMass (external)
Mass of the ejecta in the blast wave in solar masses. Default: 1
FreeExpansionRadius (external)
Initial radius of the blast wave. Default: 0.1
FreeExpansionDensity (external)
Ambient density of the problem. Default: 1
FreeExpansionEnergy (external)
Total energy of the blast wave in ergs. Default: 1e51
FreeExpansionMaxVelocity (external)
Maximum initial velocity of the blast wave (at the outer radius). If not set, a proper value is calculated using the formula in Draine & Woods (1991). Default: FLOAT_UNDEFINED
FreeExpansionTemperature (external)
Ambient temperature of the problem in K. Default: 100
FreeExapnsionBField (external)
Initial uniform magnetic field. Default: 0 0 0
FreeExpansionVelocity (external)
Initial velocity of the ambient medium. Default: 0 0 0
FreeExpansionSubgridLeft (external)
Leftmost edge of the region to set the initial refinement. Default: 0
FreeExpansionSubgridRight (external)
Rightmost edge of the region to set the initial refinement. Default: 0

### Rotating Sphere (14)¶

A test originally created to study star formation. Sets up a rotating, turbulent sphere of gas within an NFW halo. For details of the setup process, see Meece (2014).

RotatingSphereNFWMass (external)
The mass of the NFW halo within R200 in solar masses. Default: 1.0e+7 M_sun
RotatingSphereNFWConcentration (external)
The NFW Concentration parameter, defined as virial radius over scale radius (R200/Rs). Default: 2.0
RotatingSphereCoreRadius (external)
Radius of the core region in code units. The core radius is used as the break in the density profile. Gas within the core is set up in HSE, while outside the core temperature increases adiabatically with density. Default: 16 pc
RotatingSphereCentralDensity (external)
This is the scaling density for the density profile in code units. The density profile is defined as rho(r) = rho_center * (r/Rc)^-alpha * (1+r/Rc)^(alpha-beta) where rho_center is this parameters, Rc is the core radius, alpha is the core exponent (below) and beta is the outer exponent (also below). Default: 1
RotatingSphereCoreDensityExponent (external)
The density scaling exponent in the core. Within the core, density approximately goes as (r/Rc)^-alpha, were alpha is this parameter. Default: 0.1
RotatingSphereOuterDensityExponent (external)
The density scaling exponent in the outer regions. Outside of the core, density approximately goes as (r/Rc)^-beta, were alpha is this parameter. Default: 2.5
RotatingSphereExteriorTemperature (external)
This is the temperature in K of gas outside the sphere, defined as the region where density would drop below the critical density. Default: 200.0
RotatingSphereSpinParameter (external)
The Baryonic spin parameter, defined as Lambda = (J * abs(E)^(1/2)) / (G M^(5/2)), where J is the total (gas) angular momentum, E is the binding energy of the gas due to the gas and dark matter, M is the gas mas, and G is the gravitational constant. All quantities are defined relative to the edge of the sphere defined above. Default: 0.05
RotatingSphereAngularMomentumExponent (external)
This is the power law index of the scaling relation for specific angular momentum as a function of mass enclosed. l scales as (M/M_T)^chi where chi is this parameter. Default: 0.9
RotatingSphereUseTurbulence (external)
0 = No Turbulence, 1 = Use Turbulence. If using turbulence, you need a file called turbulence.in, which can be generated using the file turbulence_generator.py in the RotatingSphere problem in the run directory. Default: 0
RotatingSphereTurbulenceRMS (external)
The RMS velocity of the turbulence is normalized to some fraction of the virial sound speed of the halo, as determined from the virial temperature of the halo. This parameter is that fraction. If RotatingSphereUseTurbulence == 0, this parameters is ignored. Default: 0.01
RotatingSphereRedshift (external)
The redshift is mainly used to determine the critical density of the universe. The problem generator assumes a cosmology with Omega_L=0.7, Omega_M = 0.3, and H0 = 70 km/s/mpc. Small variations in cosmology should not have a large effect on the properties of the sphere. Default: 20.0

### Zeldovich Pancake (20)¶

A test for gas dynamics, expansion terms and self-gravity in both linear and non-linear regimes [Bryan thesis (1996), Sect. 3.3.4-3.3.5; Norman & Bryan (1998), Sect. 4]
ZeldovichPancakeCentralOffset (external)
Offset of the pancake plane. Default: 0.0 (no offset)
ZeldovichPancakeCollapseRedshift (external)
A free parameter which determines the epoch of caustic formation. Default: 1.0
ZeldovichPancakeDirection (external)
Orientation of the pancake. Type: integer. Default: 0 (along the x-axis)
ZeldovichPancakeInitialTemperature (external)
Initial gas temperature. Units: degrees Kelvin. Default: 100
ZeldovichPancakeInitialGasVelocity (external)
Initial bulk gas velocity in the direction of the pancake collapse. Units: km/s. Default: 0.0
ZeldovichPancakeInitialUniformBField (external)
Initial magnetic field. Units: Gauss. Default: 0.0 0.0 0.0
ZeldovichPancakeOmegaBaryonNow (external)
Omega Baryon at redshift z=0; standard setting. Default: 1.0
ZeldovichPancakeOmegaCDMNow (external)
Omega CDM at redshift z=0. Default: 0 (assumes no dark matter)

### Pressureless Collapse (21)¶

An 1D AMR test for the gravity solver and advection routines: the two-sided one-dimensional collapse of a homogeneous plane parallel cloud in Cartesian coordinates. Isolated boundary conditions. Gravitational constant G=1; free fall time 0.399. The expansion terms are not used in this test. (Bryan thesis 1996, Sect. 3.3.1).
PressurelessCollapseDirection (external)
Coordinate direction. Default: 0 (along the x-axis).
PressurelessCollapseInitialDensity (external)
Initial density (the fluid starts at rest). Default: 1.0

A test for time-integration accuracy of the expansion terms (Bryan thesis 1996, Sect. 3.3.3).
AdiabaticExpansionInitialTemperature (external)
Initial temperature for Adiabatic Expansion test; test example assumes 1000 K. Default: 200. Units: degrees Kelvin
AdiabaticExpansionInitialVelocity (external)
Initial expansion velocity. Default: 100. Units: km/s
AdiabaticExpansionOmegaBaryonNow (external)
Omega Baryon at redshift z=0; standard value 1.0. Default: 1.0
AdiabaticExpansionOmegaCDMNow (external)
Omega CDM at redshift z=0; default setting assumes no dark matter. Default: 0.0

### Test Gravity (23)¶

We set up a system in which there is one grid point with mass in order to see the resulting acceleration field. If finer grids are specified, the mass is one grid point on the subgrid as well. Periodic boundary conditions are imposed (gravity).
TestGravityDensity (external)
Density of the central peak. Default: 1.0
TestGravityMotionParticleVelocity (external)
Initial velocity of test particle(s) in x-direction. Default: 1.0
TestGravityNumberOfParticles (external)
The number of test particles of a unit mass. Default: 0
TestGravitySubgridLeft, TestGravitySubgridRight (external)
Start and end positions of the subgrid. Default: 0.0 and 0.0 (no subgrids)
TestGravityUseBaryons (external)
Boolean switch. Type: integer. Default: 0 (FALSE)

### Spherical Infall (24)¶

A test based on Bertschinger’s (1985) 3D self-similar spherical infall solution onto an initially overdense perturbation in an Einstein-de Sitter universe.
SphericalInfallCenter (external)
Coordinate(s) for the accretion center. Default: top grid center
SphericalInfallFixedAcceleration (external)
Boolean flag. Type: integer. Default: 0 (FALSE)
SphericalInfallFixedMass (external)
Mass used to calculate the acceleration from spherical infall (GM/(4*pi*r^3*a)). Default: If SphericalInfallFixedMass is undefined and SphericalInfallFixedAcceleration == TRUE, then SphericalInfallFixedMass = SphericalInfallInitialPerturbation * TopGridVolume
SphericalInfallInitialPerturbation (external)
The perturbation of initial mass density. Default: 0.1
SphericalInfallOmegaBaryonNow (external)
Omega Baryon at redshift z=0; standard setting. Default: 1.0
SphericalInfallOmegaCDMNow (external)
Omega CDM at redshift z=0. Default: 0.0 (assumes no dark matter) Default: 0.0
SphericalInfallSubgridIsStatic (external)
Boolean flag. Type: integer. Default: 0 (FALSE)
SphericalInfallSubgridLeft, SphericalInfallSubgridRight (external)
Start and end positions of the subgrid. Default: 0.0 and 0.0 (no subgrids)
SphericalInfallUseBaryons (external)
Boolean flag. Type: integer. Default: 1 (TRUE)

### Test Gravity: Sphere (25)¶

Sets up a 3D spherical mass distribution and follows its evolution to test the gravity solver.
TestGravitySphereCenter (external)
The position of the sphere center. Default: at the center of the domain
TestGravitySphereExteriorDensity (external)
The mass density outside the sphere. Default: tiny_number
TestGravitySphereInteriorDensity (external)
The mass density at the sphere center. Default: 1.0
TestGravitySphereRadius (external)
Radius of self-gravitating sphere. Default: 0.1
TestGravitySphereRefineAtStart (external)
Boolean flag. Type: integer. Default: 0 (FALSE)
TestGravitySphereSubgridLeft, TestGravitySphereSubgridRight (external)
Start and end positions of the subgrid. Default: 0.0 and 0.0 (no subgrids)
TestGravitySphereType (external)
Type of mass density distribution within the sphere. Options include: (0) uniform density distrubution within the sphere radius; (1) a power law with an index -2.0; (2) a power law with an index -2.25 (the exact power law form is, e.g., r-2.25, where r is measured in units of TestGravitySphereRadius). Default: 0 (uniform density)
TestGravitySphereUseBaryons (external)
Boolean flag. Type: integer . Default: 1 (TRUE)

### Gravity Equilibrium Test (26)¶

Sets up a hydrostatic exponential atmosphere with the pressure=1.0 and density=1.0 at the bottom. Assumes constant gravitational acceleration (uniform gravity field).
GravityEquilibriumTestScaleHeight (external)
The scale height for the exponential atmosphere . Default: 0.1

### Collapse Test (27)¶

A self-gravity test.
CollapseTestInitialTemperature (external)
Initial gas temperature. Default: 1000 K. Units: degrees Kelvin
CollapseTestInitialFractionHII (external)
Initial HII fraction in the domain except for the spheres. Default: 1.2e-5
CollapseTestInitialFractionHeII (external)
Initial HeII fraction in the domain except for the spheres. Default: 1e-14
CollapseTestInitialFractionHeIII (external)
Initial HeIII fraction in the domain except for the spheres. Default: 1e-17
CollapseTestInitialFractionHM (external)
Initial H- fraction in the domain except for the spheres. Default: 2e-9
CollapseTestInitialFractionH2I (external)
Initial H2I fraction in the domain except for the spheres. Default: 2e-20
CollapseTestInitialFractionH2II (external)
Initial H2II fraction in the domain except for the spheres. Default: 3e-14
CollapseTestNumberOfSpheres (external)
Number of spheres to collapse; must be <= MAX_SPHERES=10 (see Grid.h for definition). Default: 1
CollapseTestRefineAtStart (external)
Boolean flag. Type: integer. If TRUE, then initializing routine refines the grid to the desired level. Default: 1 (TRUE)
CollapseTestUseColour (external)
Boolean flag. Type: integer. Default: 0 (FALSE)
CollapseTestUseParticles (external)
Boolean flag. Type: integer. Default: 0 (FALSE)
CollapseTestSphereCoreRadius (external)
An array of core radii for collapsing spheres. Default: 0.1 (for all spheres)
CollapseTestSphereDensity (external)
An array of density values for collapsing spheres. Default: 1.0 (for all spheres)
CollapseTestSpherePosition (external)
A two-dimensional array of coordinates for sphere centers. Type: float[MAX_SPHERES][MAX_DIMENSION]. Default for all spheres: 0.5*(DomainLeftEdge[dim] + DomainRightEdge[dim])
CollapseTestSphereRadius (external)
An array of radii for collapsing spheres. Default: 1.0 (for all spheres)
CollapseTestSphereTemperature (external)
An array of temperatures for collapsing spheres. Default: 1.0. Units: degrees Kelvin
CollapseTestSphereType (external)
An integer array of sphere types. Default: 0
CollapseTestSphereVelocity (external)
A two-dimensional array of sphere velocities. Type: float[MAX_SPHERES][MAX_DIMENSION]. Default: 0.0
CollapseTestUniformVelocity (external)
Uniform velocity. Type: float[MAX_DIMENSION]. Default: 0 (for all dimensions)
CollapseTestSphereMetallicity (external)
Metallicity of the sphere in solar metallicity. Default: 0.
CollapseTestFracKeplerianRot (external)
Rotational velocity of the sphere in units of Keplerian velocity, i.e. 1 is rotationally supported. Default: 0.
CollapseTestSphereTurbulence (external)
Turbulent velocity field sampled from a Maxwellian distribution with the temperature specified in CollapseTestSphereTemperature This parameter multiplies the turbulent velocities by its value. Default: 0.
CollapseTestSphereDispersion (external)
If using particles, this parameter multiplies the velocity dispersion of the particles by its value. Only valid in sphere type 8 (cosmological collapsing sphere from a uniform density). Default: 0.
CollapseTestSphereCutOff (external)
At what radius to terminate a Bonner-Ebert sphere. Units? Default: 6.5
CollapseTestSphereAng1 (external)
Controls the initial offset (at r=0) of the rotational axis. Units in radians. Default: 0.
CollapseTestSphereAng2 (external)
Controls the outer offset (at r=SphereRadius of the rotational axis. In both CollapseTestSphereAng1 and CollapseTestSphereAng2 are set, the rotational axis linearly changes with radius between CollapseTestSphereAng1 and CollapseTestSphereAng2. Units in radians. Default: 0.
CollapseTestSphereConstantPressure (external)
Constant pressure inside the sphere that is equal to the pressure at the outer radius. Default: 0
CollapseTestSphereSmoothSurface (external)
The density interface between the ambient and sphere medium is smoothed with a hyperbolic tangent. Default: 0
CollapseTestSmoothRadius (external)
The outer radius of the smoothed interface. This parameter is in units of the sphere radius. Default: 1.2
CollapseTestSphereHIIFraction (external)
Initial HII fraction of the sphere. Default: 1.2e-5
CollapseTestSphereHeIIFraction (external)
Initial HeII fraction of the sphere. Default: 1e-14
CollapseTestSphereHeIIIFraction (external)
Initial HeIII fraction of the sphere. Default: 1e-17
CollapseTestSphereHMFraction (external)
Initial H- fraction of the sphere. Default: 2e-9
CollapseTestSphereH2IFraction (external)
Initial H2I fraction of the sphere. Default: 2e-20
CollapseTestSphereH2IIFraction (external)
Initial H2II fraction of the sphere. Default: 3e-14
CollapseTestSphereInitialLevel (external)
Failed experiment to try to force refinement to a specified level. Not working. Default: 0
CollapseTestWind (external)
Boolean flag. Type: integer. This parameter decides if there is wind (inflow boundary). Default: 0 (FALSE)
CollapseTestWindVelocity (external)
When using inflow boundary, this is the inflow velocity. Default: 0.

### Test Gravity Motion (28)¶

TestGravityMotionParticleVelocity (external)
Initial velocity for particle. Default: 1.0

### Test Orbit (29)¶

TestOrbitNumberOfParticles (external)
Number of test particles. Default: 1
TestOrbitRadius (external)
Initial radius of orbit. Default: 0.2
TestOrbitCentralMass (external)
Central mass. Default: 1.0
TestOrbitTestMass (external)
Mass of the test particle. Default: 1.0e-6
TestOrbitUseBaryons (external
Boolean flag. (not implemented) Default: FALSE

### Cosmology Simulation (30)¶

A sample cosmology simulation.
CosmologySimulationDensityName (external)
This is the name of the file which contains initial data for baryon density. Type: string. Example: GridDensity. Default: none
CosmologySimulationTotalEnergyName (external)
This is the name of the file which contains initial data for total energy. Default: none
CosmologySimulationGasEnergyName (external)
This is the name of the file which contains initial data for gas energy. Default: none
CosmologySimulationVelocity[123]Name (external)
These are the names of the files which contain initial data for gas velocities. Velocity1 - x-component; Velocity2 - y-component; Velocity3 - z-component. Default: none
CosmologySimulationParticleMassName (external)
This is the name of the file which contains initial data for particle masses. Default: none
CosmologySimulationParticlePositionName (external)
This is the name of the file which contains initial data for particle positions. Default: none
CosmologySimulationParticleVelocityName (external)
This is the name of the file which contains initial data for particle velocities. Default: none
CosmologySimulationParticleVelocity[123]Name (external) This is
the name of the file which contains initial data for particle velocities but only has one component per file. This is more useful with very large (>=20483) datasets. Currently one can only use this in conjunction with CosmologySimulationCalculatePositions. because it expects a 3D grid structure instead of a 1D list of particles. Default: None.
CosmologySimulationCalculatePositions (external)
If set to 1, Enzo will calculate the particle positions in one of two ways: 1) By using a linear Zeldo’vich approximation based on the particle velocities and a displacement factor [dln(growth factor) / dtau, where tau is the conformal time], which is stored as an attribute in the initial condition files, or 2) if the user has also defined either CosmologySimulationParticleDisplacementName or CosmologySimulationParticleDisplacement[123]Name, by reading in particle displacements from an external code and applying those directly. The latter allows the use of non-linear displacements. Default: 0.
CosmologySimulationParticleDisplacementName (external)
This is the name of the file which contains initial data for particle displacements. Default: none
CosmologySimulationParticleDisplacement[123]Name (external) This
is the name of the file which contains initial data for particle displacements but only has one component per file. This is more useful with very large (>=20483) datasets. Currently one can only use this in conjunction with CosmologySimulationCalculatePositions. because it expects a 3D grid structure instead of a 1D list of particles. Default: None.
CosmologySimulationNumberOfInitialGrids (external)
The number of grids at startup. 1 means top grid only. If >1, then nested grids are to be defined by the following parameters. Default: 1
CosmologySimulationSubgridsAreStatic (external)
Boolean flag, defines whether the subgrids introduced at the startup are static or not. Type: integer. Default: 1 (TRUE)
CosmologySimulationGridLevel (external)
An array of integers setting the level(s) of nested subgrids. Max dimension MAX_INITIAL_GRIDS is defined in CosmologySimulationInitialize.C as 10. Default for all subgrids: 1, 0 - for the top grid (grid #0)
CosmologySimulationGridDimension[#] (external)
An array (arrays) of 3 integers setting the dimensions of nested grids. Index starts from 1. Max number of subgrids MAX_INITIAL_GRIDS is defined in CosmologySimulationInitialize.C as 10. Default: none
CosmologySimulationGridLeftEdge[#] (external)
An array (arrays) of 3 floats setting the left edge(s) of nested subgrids. Index starts from 1. Max number of subgrids MAX_INITIAL_GRIDS is defined in CosmologySimulationInitialize.C as 10. Default: none
CosmologySimulationGridRightEdge[#] (external)
An array (arrays) of 3 floats setting the right edge(s) of nested subgrids. Index starts from 1. Max number of subgrids MAX_INITIAL_GRIDS is defined in CosmologySimulationInitialize.C as 10. Default: none
CosmologySimulationUseMetallicityField (external)
Boolean flag. Type: integer. Default: 0 (FALSE)
CosmologySimulationInitialFractionH2I (external)
The fraction of molecular hydrogen (H_2) at InitialRedshift. This and the following chemistry parameters are used if MultiSpecies is defined as 1 (TRUE). Default: 2.0e-20
CosmologySimulationInitialFractionH2II (external)
The fraction of singly ionized molecular hydrogen (H2+) at InitialRedshift. Default: 3.0e-14
CosmologySimulationInitialFractionHeII (external)
The fraction of singly ionized helium at InitialRedshift. Default: 1.0e-14
CosmologySimulationInitialFractionHeIII (external)
The fraction of doubly ionized helium at InitialRedshift. Default: 1.0e-17
CosmologySimulationInitialFractionHII (external)
The fraction of ionized hydrogen at InitialRedshift. Default: 1.2e-5
CosmologySimulationInitialFractionHM (external)
The fraction of negatively charged hydrogen (H-) at InitialRedshift. Default: 2.0e-9
CosmologySimulationInitialFractionMetal (external)
The fraction of metals at InitialRedshift. Default: 1.0e-10
CosmologySimulationInitialTemperature (external)
A uniform temperature value at InitialRedshift (needed if the initial gas energy field is not supplied). Default: 550*((1.0 + InitialRedshift)/201)2
CosmologySimulationOmegaBaryonNow (external)
This is the contribution of baryonic matter to the energy density at the current epoch (z=0), relative to the value required to marginally close the universe. Typical value 0.06. Default: 1.0
CosmologySimulationOmegaCDMNow (external)
This is the contribution of CDM to the energy density at the current epoch (z=0), relative to the value required to marginally close the universe. Typical value 0.24. Default: 0.0 (no dark matter)
CosmologySimulationManuallySetParticleMassRatio (external)
This binary flag (0 - off, 1 - on) allows the user to manually set the particle mass ratio in a cosmology simulation. Default: 0 (Enzo automatically sets its own particle mass)
CosmologySimulationManualParticleMassRatio (external)
This manually controls the particle mass in a cosmology simulation, when CosmologySimulationManuallySetParticleMassRatio is set to 1. In a standard Enzo simulation with equal numbers of particles and cells, the mass of a particle is set to CosmologySimulationOmegaCDMNow/CosmologySimulationOmegaMatterNow, or somewhere around 0.85 in a WMAP-type cosmology. When a different number of particles and cells are used (128 particles along an edge and 256 cells along an edge, for example) Enzo attempts to calculate the appropriate particle mass. This breaks down when ParallelRootGridIO and/or ParallelParticleIO are turned on, however, so the user must set this by hand. If you have the ratio described above (2 cells per particle along each edge of a 3D simulation) the appropriate value would be 8.0 (in other words, this should be set to (number of cells along an edge) / (number of particles along an edge) cubed. Default: 1.0.

### Isolated Galaxy Evolution (31)¶

Initializes an isolated galaxy, as per the Tasker & Bryan series of papers.
GalaxySimulationRefineAtStart (external)
Controls whether or not the simulation is refined beyond the root grid at initialization. (0 - off, 1 - on). Default: 1
GalaxySimulationInitialRefinementLevel (external)
Level to which the simulation is refined at initialization, assuming GalaxySimulationRefineAtStart is set to 1. Default: 0
GalaxySimulationSubgridLeft, GalaxySimulationSubgridRight (external)
Vectors of floats defining the edges of the volume which is refined at start. No default value.
GalaxySimulationUseMetallicityField (external)
Turns on (1) or off (0) the metallicity field. Default: 0
GalaxySimulationInitialTemperature (external)
Initial temperature that the gas in the simulation is set to. Default: 1000.0
GalaxySimulationUniformVelocity (external)
Vector that gives the galaxy a uniform velocity in the ambient medium. Default: (0.0, 0.0, 0.0)
GalaxySimulationDiskRadius (external)
Radius (in Mpc) of the galax disk. Default: 0.2
GalaxySimulationGalaxyMass (external)
Dark matter mass of the galaxy, in Msun. Needed to initialize the NFW gravitational potential. Default: 1.0e+12
GalaxySimulationGasMass (external)
Amount of gas in the galaxy, in Msun. Used to initialize the density field in the galactic disk. Default: 4.0e+10
GalaxySimulationDiskPosition (external)
Vector of floats defining the center of the galaxy, in units of the box size. Default: (0.5, 0.5, 0.5)
GalaxySimulationDiskScaleHeightz (external)
Disk scale height, in Mpc. Default: 325e-6
GalaxySimulationDiskScaleHeightR (external)
Disk scale radius, in Mpc. Default: 3500e-6
GalaxySimulationDarkMatterConcentrationParameter (external)
NFW dark matter concentration parameter. Default: 12.0
GalaxySimulationDiskTemperature (external)
Temperature of the gas in the galactic disk. Default: 1.0e+4
GalaxySimulationInflowTime (external)
Controls inflow of gas into the box. It is strongly suggested that you leave this off. Default: -1 (off)
GalaxySimulationInflowDensity (external)
Controls inflow of gas into the box. It is strongly suggested that you leave this off. Default: 0.0
GalaxySimulationAngularMomentum (external)
Unit vector that defines the angular momentum vector of the galaxy (in other words, this and the center position define the plane of the galaxy). This _MUST_ be set! Default: (0.0, 0.0, 0.0)
GalaxySimulationRPSWind (external)
This flag turns on the ram pressure stripped (RPS) wind in the GalaxySimulation problem and sets the mode. 0 = off, 1 = on with simple constant wind values, 2 = on with RPS values set from a file with the name ICMinflow_data.in. For the file input case, the file should consist of a set of lines with each line specifying a 6 columns consisting of time, wind density, wind temperature, wind x/y/z velocity. All units in the file are assumed to be CGS and wind values are applied at the time indicated to the corner of the box, with linear interpolation between key frames. See Salem et al. (2015) for a worked example. Default: 0
GalaxySimulationRPSWindShockSpeed (external)
This is speed of the RPS driven shock (which differs from the wind velocity), to be used to determine where and when to apply the appropriate wind boundary condition on the boundary. Code units. Default: 0.0
GalaxySimulationRPSWindDelay (external)
This is a delay (in code units) for the RPS wind to be applied (for example to give time for the galaxy to relax). Default: 0.0
GalaxySimulationRPSWindDensity (external)
For case 1, this is the density of the RPS wind, in code units. Default: 1.0
GalaxySimulationRPSWindtotalEnergy (external)
For case 1, this is the total energy of the RPS wind, in code units. Default: 1.0
GalaxySimulationRPSWindPressure (external)
For case 1, this is the pressutre of the RPS wind (unused). Default: 1.0
GalaxySimulationRPSWindVelocity (external)
For case 1, This is the wind velocity (code units) Default: 0 0 0
GalaxySimulationRPSWindPreWindDensity (external)
This is the density applied to the boundary before the wind arrives. Default: 1.0
GalaxySimulationRPSWindPreWindTotalEnergy (external)
This is the total energy applied to the boundary before the wind arrives. Default: 1.0
GalaxySimulationRPSWindPreWindVelocity (external)
This is the velocity vector applied to the boundary before the wind arrives. Default:

### Shearing Box Simulation (35)¶

ShearingBoxProblemType (external)
Value of 0 starts a sphere advection through the shearing box test. Value of 1 starts a standard Balbus & Hawley shearing box simulation. Default: 0
ShearingBoxRefineAtStart (external)
Refine the simulation at start. Default: 1.0
ThermalMagneticRatio (external)
Plasma beta (Pressure/Magnetic Field Energy) Default: 400.0
FluctuationAmplitudeFraction (external)
The magnitude of the sinusoidal velocity perturbations as a fraction of the angular velocity. Default: 0.1
ShearingBoxGeometry (external)
Defines the radius of the sphere for ShearingBoxProblemType = 0, and the frequency of the velocity fluctuations (in units of 2pi) for ShearingBoxProblemType = 1. Default: 2.0

### Supernova Restart Simulation (40)¶

All of the supernova parameters are to be put into a restart dump parameter file. Note that ProblemType must be reset to 40, otherwise these are ignored.
SupernovaRestartEjectaCenter[#] (external)
Input is a trio of coordinates in code units where the supernova’s energy and mass ejecta will be centered. Default: FLOAT_UNDEFINED
SupernovaRestartEjectaEnergy (external)
The amount of energy instantaneously output in the simulated supernova, in units of 1e51 ergs. Default: 1.0
SupernovaRestartEjectaMass (external)
The mass of ejecta in the supernova, in units of solar masses. Default: 1.0
SupernovaRestartEjectaRadius (external)
The radius over which the above two parameters are spread. This is important because if it’s too small the timesteps basically go to zero and the simulation takes forever, but if it’s too big then you loose information. Units are parsecs. Default: 1.0 pc
SupernovaRestartName (external)
This is the name of the restart data dump that the supernova problem is initializing from.
SupernovaRestartColourField
Reserved for future use.

### Photon Test (50)¶

This test problem is modeled after Collapse Test (27), and thus borrows all of its parameters that control the setup of spheres. Replace CollapseTest with PhotonTest in the sphere parameters, and it will be recognized. However there are parameters that control radiation sources, which makes this problem unique from collapse test. The radiation sources are fixed in space.
PhotonTestNumberOfSources (external)
Sets the number of radiation sources. Default: 1.
PhotonTestSourceType (external)
Sets the source type. No different types at the moment. Default: 0.
PhotonTestSourcePosition (external)
Sets the source position. Default: 0.5*(DomainLeftEdge + DomainRightEdge)
PhotonTestSourceLuminosity (external)
Sets the source luminosity in units of photons per seconds. Default: 0.
PhotonTestSourceLifeTime (external)
Sets the lifetime of the source in units of code time. Default: 0.
PhotonTestSourceRampTime (external)
If non-zero, the source will exponentially increase its luminosity until it reaches the full luminosity when the age of the source equals this parameter. Default: 0.
PhotonTestSourceEnergyBins (external)
Sets the number of energy bins in which the photons are emitted from the source. Default: 4.
PhotonTestSourceSED (external)
An array with the fractional luminosity in each energy bin. The sum of this array must equal to one. Default: 1 0 0 0
PhotonTestSourceEnergy (external)
An array with the mean energy in each energy bin. Units are in eV. Default: 14.6 25.6 56.4 12.0 (i.e. HI ionizing, HeI ionizing, HeII ionizing, Lyman-Werner)
PhotonTestSourceType (external)
Indicates what radiation type (1 = isotropic, -2 = Beamed, -3 = Episodic). Default: 0
PhotonTestSourceOrientation (external)
Normal direction in Cartesian axes of beamed radiation (type = -2). Default = 0 0 1
PhotonTestInitialFractionHII (external)
Sets the initial ionized fraction of hydrogen. Default: 1.2e-5
PhotonTestInitialFractionHeII (external)
Sets the initial singly-ionized fraction of helium. Default: 1e-14
PhotonTestInitialFractionHeIII (external)
Sets the initial doubly-ionized fraction of helium. Default: 1e-17
PhotonTestInitialFractionHM (external)
Sets the initial fraction of H-. Default: 2e-9
PhotonTestInitialFractionH2I (external)
Sets the initial neutral fraction of H2. Default: 2e-20
PhotonTestInitialFractionH2II (external)
Sets the initial ionized fraction of H2. Default: 3e-14
PhotonTestOmegaBaryonNow (obsolete)
Default: 0.05.
PhotonTestDensityFilename (external)
Filename of an external density field in HDF5 format. The file should only have one dataset. Default: (undefined)
PhotonTestHIIFractionFilename (external)
Filename of an external HII fraction field in its own HDF5 format. The file should only have one dataset. Default: (undefined)
PhotonTestHeIIFractionFilename (external)
Filename of an external HeII fraction field in its own HDF5 format. The file should only have one dataset. Default: (undefined)
PhotonTestHeIIIFractionFilename (external)
Filename of an external HeIII fraction field in its own HDF5 format. The file should only have one dataset. Default: (undefined)
PhotonTestTemperatureFilename (external)
Filename of an external temperature field in its own HDF5 format. The file should only have one dataset. Default: (undefined)

### Turbulence Simulation with Stochastic Forcing (59)¶

Typical quasi-isothermal “turbulence-in-a-box” problem with non-static driving field. For details on stochastic forcing, see Schmidt et al. 2009 A&A 494, 127-145 http://dx.doi.org/10.1051/0004-6361:200809967

3D simulations with MUSCL hydro and MHD solver are tested. PPM, ZEUS and MHDCT unsupported at this time.

Remember that in addition to the problem specific parameters below UseDrivingField = 1 has to be turned on!

DrivenFlowProfile (external)
Shape of forcing power spectrum (1: delta peak, 2: band, 3: parabolic window).
DrivenFlowAlpha (external)
Ratio of domain length to integral length for each dimension (L = X/alpha).
DrivenFlowBandWidth (external)
Determines band width of the forcing spectrum relative to alpha (maximal value = 1).
DrivenFlowMach (external)
Characteristic velocity scale for each dimension (charcteristic force per unit mass F = V*V/L).
DrivenFlowAutoCorrl (external)
Determines autocorrelation time of the stochastic force in units of the integral time scale T = L/V.
DrivenFlowWeight (external)
Determines weight of solenoidal relative to dilatational modes (1 = purely solenoidal, 0 = purely dilatational).
DrivenFlowSeed (external)
Seed of random number generator.
DrivenFlowDensity (external)
Initial uniform density.
DrivenFlowPressure (external)
Initial uniform pressure.
DrivenFlowMagField (external)
Initial uniform magnetic field (x-direction)

### Turbulence Simulation (60)¶

Quasi-isothermal forced turbulence.

TurbulenceSimulationsDensityName (external)

TurbulenceSimulationTotalEnergyName (external)

TurbulenceSimulationGasPressureName (external)

TurbulenceSimulationGasEnergyName (external)

TurbulenceSimulationVelocityName (external)

TurbulenceSimulationRandomForcingName (external)

TurbulenceSimulationMagneticName (external)

TurbulenceSimulationInitialTemperature (external)

TurbulenceSimulationInitialDensity (external)

TurbulenceSimulationSoundSpeed (external)

TurbulenceSimulationInitialPressure (external)

TurbulenceSimulationInitialDensityPerturbationAmplitude (external)

TurbulenceSimulationNumberOfInitialGrids (external)
Default: 1
TurbulenceSimulationSubgridsAreStatic (external)
Boolean flag. Default: 1
TurbulenceSimulationGridLeftEdge[] (external)
TBD
TurbulenceSimulationGridRightEdge[] (external)
TBD
TurbulenceSimulationGridDimension[] (external)
TBD
TurbulenceSimulationGridLevel[] (external)
TBD
TurbulenceSimulationInitialMagneticField[i] (external)
Initial magnetic field strength in the ith direction. Default: 5.0 (all)
RandomForcing (external)
This parameter is used to add random forcing field to create turbulence; see Mac Low 1999, ApJ 524, 169. Default: 0
RandomForcingEdot (external)
This parameter is used to define the value of such field; see TurbulenceSimulationInitialize.C and ComputeRandomForcingNormalization.C. Default: -1.0
RandomForcingMachNumber (external)
This parameter is used to define the value of such field; see Grid_TurbulenceSimulationInitialize.C and Grid_ComputeRandomForcingFields.C. Default: 0.0
CycleSkipGlobalDataDump (external)
Cycles to skip before global data (defined in ComputeRandomForcingNormalization.C) is dumped.

### Protostellar Collapse (61)¶

Bate 1998, ApJL 508, L95-L98
ProtostellarCollapseCoreRadius (external)
Radius of the core. Default: 0.005
ProtostellarCollapseOuterDensity (external)
Initial density. Default: 1.0
ProtostellarCollapseAngularVelocity (external)
Initial angular velocity. Default: 0
ProtostellarCollapseSubgridLeft, ProtostellarCollapseSubgridRight (external)
Start and end position of subgrid. Default: 0 (for both)

### Cooling Test (62)¶

This test problem sets up a 3D grid varying smoothly in log-space in H number density (x dimension), metallicity (y-dimension), and temperature (z-dimension). The hydro solver is turned off. By varying the RadiativeCooling and CoolingTestResetEnergies parameters, two different cooling tests can be run. 1) Keep temperature constant, but iterate chemistry to allow species to converge. This will allow you to make plots of Cooling rate vs. T. For this, set RadiativeCooling to 0 and CoolingTestResetEnergies to 1. 2) Allow gas to cool, allowing one to plot Temperature vs. time. For this, set RadiativeCooling to 1 and CoolingTestResetEnergies to 0.
CoolingTestMinimumHNumberDensity (external)
The minimum density in code units at x=0. Default: 1 [cm-3].
CoolingTestMaximumHNumberDensity (external)
The maximum density in code units at x=DomainRightEdge[0]. Default: 1e6 [cm-3].
CoolingTestMinimumMetallicity (external)
The minimum metallicity at y=0. Default: 1e-6 [Zsun].
CoolingTestMaximumMetallicity (external)
The maximum metallicity at y=DomainRightEdge[1]. Default: 1 [Zsun].
CoolingTestMinimumTemperature (external)
The minimum temperature in Kelvin at z=0. Default: 10.0 [K].
CoolingTestMaximumTemperature (external)
The maximum temperature in Kelvin at z=DomainRightEdge[2]. Default: 1e7 [K].
CoolingTestResetEnergies (external)
An integer flag (0 or 1) to determine whether the grid energies should be continually reset after every iteration of the chemistry solver such that the temperature remains constant as the mean molecular weight varies slightly. Default: 1.

### 3D Collapse Test (101)¶

NumberOfSpheres (external) RefineAtStart UseParticles MediumDensity MediumPressure UniformVelocity SphereType[] SphereRadius[] SphereCoreRadius[] SphereDensity[] SpherePressure[] SphereSoundVelocity[] SpherePosition[] SphereVelocity[] SphereAngVel[] SphereTurbulence[] SphereCutOff[] SphereAng1[] SphereAng2[] SphereNumShells[]

### 1D Spherical Collapse Test (102)¶

RefineAtStart (external)
Boolean flag. Default: TRUE
UseParticles (external)
Boolean flag. Default: False
MediumDensity (external)
Initial density of the medium. Default: 1.0
MediumPressure (external)
Initial pressure of the medium. Default: 1.0
SphereType (external)
Default: 0
SphereRadius (external)
Radius of the sphere. Default: 1.0
SphereCoreRadius (external)
Radius of the core. Default: 0
SphereDensity (external)
Initial density of the sphere. Default: 1.0
SpherePressure (external)
Initial pressure of the sphere. Default: 1.0
SphereSoundVelocity (external)
Velocity of sound. Default: 1.0
SphereAngVel (external)
Angular velocity of the sphere. Default: 0.0

### Hydro and MHD Turbulence Simulation (106)¶

RefineAtStart (external)
Boolean flag. Default: TRUE
PutSink (external)
Boolean flag. Default: FALSE
Density (external)
Boolean flag. Default: TRUE
SoundVelocity (external)
Velocity of sound. Default: 1.0
MachNumber (external)
Default: 1.0
AngularVelocity (external)
Default: 0
CloudRadius (external)
Initial radius of the cloud. Default: 0.05
SetTurbulence (external)
Boolean flag. Default: TRUE
InitialBfield (external)
Initial magnetic field strength. Default: 0
RandomSeed (external)
Default: 52761
CloudType (external)
Default: 1

### Put Sink from Restart (107)¶

PutSinkRestartName (external)
Filename to restart from.

### Cluster Cooling Flow (108)¶

ClusterSMBHFeedback (external)
Boolean flag. Default: FALSE
ClusterSMBHJetMdot (external)
Mdot of one Jet. Units: Solar mass per year. Default: 3.0
ClusterSMBHJetVelocity (external)
Units:km/s. Default: 10000.0
ClusterSMBHJetRadius (external)
The radius of the jet launching region. Units: cell width. Default: 6.0
ClusterSMBHJetLaunchOffset (external)
The distance of the jet launching plane to the center of the cluster. Units: cell width. Default: 10.0
ClusterSMBHStartTime (external)
The time to start feedback in code unit. Default: 1.0
ClusterSMBHTramp (external)
The ramp time in Myr. Default: 0.1
ClusterSMBHJetOpenAngleRadius (external)
Default: 0.0
ClusterSMBHFastJetRadius (external)
Default: 0.1
ClusterSMBHFastJetVelocity (external)
Unit: km/s. Default: 10000.0
ClusterSMBHJetEdot (external)
Unit: 10^44 ergs/s. Default: 1.0
ClusterSMBHKineticFraction (external)
The fraction of kinetic energy feedback; the rest is thermal feedback. Default: 1.0
ClusterSMBHJetAngleTheta (external)
The angle of the jet direction with respect to z-axis. Default: 0.0 (along the axis)
ClusterSMBHJetAnglePhi (external)
Default: 0.0
ClusterSMBHJetPrecessionPeriod (external)
Unit: Myr. Default: 0.0 (not precessing)
ClusterSMBHCalculateGasMass (external)
Type: integer. 1–Calculate the amount of cold gas around the SMBH and remove it at the rate of 2*Mdot; 2–Calculate Mdot based on the amount of cold gas around the SMBH; 3–Calculate Mdot similar to 2 but change ClusterSMBHJetDim periodically (period = ClusterSMBHJetPrecessionPeriod); 4–Calculate Mdot within Bondi radius (only use this when Bondi radius is resolved); 0–off (do not remove cold gas). Default: 1.
ClusterSMBHFeedbackSwitch (external)
Boolean flag. When ClusterSMBHCalculateGasMass=1, ClusterSMBHFeedbackSwitch is turned on when there is enough cold gas (ClusterSMBHEnoughColdGas) around the SMBH. Default: FALSE
ClusterSMBHEnoughColdGas (external)
Unit: Solar mass. Default: 1.0e7
ClusterSMBHAccretionTime (external)
When ClusterSMBHCalculateGasMass = 2, Mdot = Mcold/ClusterSMBHAccretionTime. Default: 5.0 (Myr)
ClusterSMBHJetDim (external)
0–x; 1–y; 2–z. Default: 2
ClusterSMBHAccretionEpsilon (external)
Jet Edot = ClusterSMBHAccretionEpsilon * Mdot * c^2. Default: 0.001
ClusterSMBHDiskRadius (external)
The size of the accretion zone in kpc. Default: 0.5
ClusterSMBHBCG (external)
The stellar component of the Perseus BCG (in cluster simulations) or the elliptical galaxies (in simulations of isolated elliptical galaxies). Default: 1.0
ClusterSMBHMass (external)
The mass of the SMBH of the Perseus BCG (in cluster simulations) or the elliptical galaxies (in simulations of isolated elliptical galaxies). Default: 0
EllipticalGalaxyRe (external)
Re is the radius of the isophote enclosing half of the galaxy’s light. In Herquist profile, a=Re/1.8153. Default: 0
OldStarFeedbackAlpha (external)
Mass ejection rate from evolved stars in the unit of 10^{-19} s^{-1}. It is typically within a factor of 2 of unity. Default: 0
SNIaFeedbackEnergy (external)
Energy feedback from evolved stars (Type Ia SN). Default: 1.0

### Light Boson Initialize¶

LightBosonProblemType (external)
Indicates the type of test to be run for a 1D Schrodinger problem (FDM). Options are: (1) A single Gaussian density field; (2) A Fresnel test problem; (3) a Zeldovich collapse test; (4) two colliding Gaussian packets. Default: 1
LightBosonCenter (external)
Specifies center position for the tests. Default: 0.5

### FDM Collapse¶

No parameters. Assumes there are files called GridDensity.new containing the density field, and GridRePsi and GridImPsi which contain the real and imaginary parts of the wave function. There is a python code in run/FuzzyDarkMatter/init.py which generates a

### 1D MHD Test (200)¶

RefineAtStart (external)
Boolean flag. Default: TRUE
LeftVelocityX, RightVelocityX (external)
Initial velocity x-direction. Default: 0 (for both)
LeftVelocityY, RightVelocityY (external)
Initial velocity y-direction. Default: 0 (for both)
LeftVelocityZ, RightVelocityZ (external)
Initial velocity z-direction. Default: 0 (for both)
LeftPressure, RightPressure (external)
Initial pressure. Default: 1.0 (for both)
LeftDensity, RightDensity (external)
Initial density. Default: 1.0 (for both)
LeftBx, RightBx (external)
Initial magnetic field x-direction. Default: 0 (for both)
LeftBy, RightBy (external)
Initial magnetic field y-direction. Default: 0 (for both)
LeftBz, RightBz (external)
Initial magnetic field z-direction. Default: 0 (for both)

### 2D MHD Test (201)¶

This problem type sets up many common 2D hydro and MHD problem types. Many of them can be run also without MHD despite the name. Which problem is done is controled by MHD2DProblemType which can vary from 0 to 16 so far.

RefineAtStart (external)
Boolean flag. Default: TRUE
LowerVelocityX, UpperVelocityX (external)
Initial velocity x-direction. Default: 0 (for both)
LowerVelocityY, UpperVelocityY (external)
Initial velocity y-direction. Default: 0 (for both)
LowerPressure, UpperPressure (external)
Initial pressure. Default: 1.0 (for both)
LowerDensity, UpperDensity (external)
Initial density. Default: 1.0 (for both)
LowerBx, UpperBx (external)
Initial magnetic field x-direction. Default: 0 (for both)
LowerBy, UpperBy (external)
Initial magnetic field y-direction. Default: 0 (for both)
MHD2DProblemType (external)
Default: 0 0: Raleigh-Taylor, 1: MHD rotor (Toth 2000, JCompPhys 161, 605.), 2: MHD blast wave (Gardiner and Stone 2005, JCompPhys. 205, 509), 3: MHD Kelvin-Helmholtz (Gardiner & Stone 2005), 4: Another MHD Kelvin Helmholtz, 5: Shock-vortex interaction (Rault, Chiavassa & Donat, 2003, J. Scientific Computing, 19, 1.), 6: Sedov-Taylor Blast Wave (Fryxell et al. 2000, ApJS, 131, 273), 7: Cylindrical Sedov-Taylor Blast Wave (Fryxell et al. 2000), 8: Like MHD2DProblemType = 5 but with a small perturbation upstream of the shock to test odd even coupling of Reimann Solvers, 9: Smoothed Kelvin Helnholtz problem (Robertson, Kravtsov, Gnedin, Abel & Rudd 2010, MNRAS, 401), 10: A modified Raleigh-Taylor problem, 11: Uniform density with sinusoidal shear velocity (Compare to rpSPH tests in Abel 2012), 12: Experimental test, 13: Exploratory blob test, 14: Wengen 2 test to study colliding flows with very soft equations of state, 15: Another experiment with B-fields, 16: A validated non-linear Kelvin Helmholtz test (Lecoanet, McCourt, Quataert, Burns, Vasil, Oishi, Brown, Stone, & O’Leary 2015 preprint)
RampWidth (external)
Default: 0.05
UserColour (external)
Boolean flag. Default: FALSE

### 3D MHD Collapse Test (202)¶

RefineAtStart (external)
Boolean flag. Default: FALSE
LowerVelocityX, UpperVelocityX (external)
Initial velocity x-direction. Default: 0 (for both)
LowerVelocityY, UpperVelocityY (external)
Initial velocity y-direction. Default: 0 (for both)
LowerPressure, UpperPressure (external)
Initial pressure. Default: 1.0 (for both)
LowerDensity, UpperDensity (external)
Initial density. Default: 1.0 (for both)
LowerBx, UpperBx (external)
Initial magnetic field x-direction. Default: 0 (for both)
LowerBy, UpperBy (external)
Initial magnetic field y-direction. Default: 0 (for both)
MHD3DProblemType (external)
Default: 0

### MHD Turbulent Collapse Test (203)¶

RefineAtStart (external)
Boolean flag. Default: TRUE
Density (external)
Initial density. Default: 1.0
SoundVelocity (external)
Speed of sound. Default: 1.0
MachNumber (external)
Default: 1.0
InitialBfield (external)
Initial magnetic field strength. Default: 0
RandomSeed (external)
Default: 0

### Galaxy Disk (207)¶

NumberOfHalos (external)
Number of Halos simulated. Default: 1
RefineAtStart (external)
Boolean flag. Default: TRUE
UseParticles (external)
Boolean flag. Default: FALSE
UseGas (external)
Boolean flag. Default: TRUE
MediumTemperature (external)
Temperature of the medium. Default: 1000
MediumDensity (external)
Density of the medium. Default: 1.0
HaloMagneticField (external)
Magnetic Field Strength. Default: 0
UniformVelocity[i] (external)
Velocity in all 3 dimensions. Default: 0 (all)
GalaxyType[i] (external)
Sppecifying galaxy type for the ith sphere. Default: 0 (all)
HaloRadius[i] (external)
Radius of the halo for the ith sphere. Default: 1 (all)
HaloCoreRadius[i] (external)
Core radius for the ith sphere. Default: 0.1 (all)
HaloDensity[i] (external)
Density of the halo for the ith sphere. Default: 1 (all)
HaloTemperature[i] (external)
Temperature of the halo for the ith sphere. Default: 1 (all)
HaloAngVel[i] (external)
TBD
HaloSpin[i] (external)
TBD
HaloPosition[i][j] (external)
Position of the Halo.
HaloVelocity[i][j] (external)
Velocity of the Halo.
DiskRadius[i] (external)
TBD
DiskHeight[i] (external)
TBD
DiskDensity[i] (external)
TBD
DiskTemperature[i] (external)
TBD
DiskMassFraction[i] (external)
Default: 0 (all)
DiskFlaringParameter[i] (external)
Default: 10 (all)

### AGN Disk (207)¶

DiskType (external)
Default: 1
RefineAtStart (external)
Boolean flag. Default: 0
BlackHoleMass (external)
Initial mass of black hole. Default: 0
UseGas (external)
Boolean flag. Default: 1
DiskDensity (external)
Initial density of the disk. Default: 1
DiskTemperature (external)
Initial temperature of the disk. Default: 1
DiskRadius (external)
Initial radius of the disk. Default: 1
DiskHeight (external)
Initial height of the disk. Default: 1

### CR Shock Tube (250: unigrid and AMR)¶

Very similar to normal shock tube (see problem 1) but includes CR component. See Salem, Bryan & Hummels (2014) for discussion.

HydroShockTubesLeftCREnDensity, HydroShockTubesRightCREnDensity (external)
The initial CR energy density on the left and right sides. Default: 1.0 for each value.

HydroShockTubesCenterDensity, HydroShockTubesCenterPressure, HydroShockTubesCenterVelocityX, HydroShockTubesCenterVelocityY, HydroShockTubesCenterVelocityZ, HydroShockTubesCenterCREnDensity (external)

In addition to setting a shock tube with two constant regions, this version also allows for three constant regions, with a Center region in addition to the Left and Right regions. Finally, there are two special cases – if HydroShockTubesCenterCREnDensity is set to 123.4, then the central region will be set to a ramp between the left and right regions, and if HydroShockTubesCenterCREnDensity is set to 567.8, then a gaussian CR energy density is initialized (these problems were set up to test the CR diffusion).

### Poisson Solver Test (300)¶

PoissonSolverTestType (external)
Default: 0
PoissonSolverTestGeometryControl (external)
Default: 1
PoissonSolverTestRefineAtStart (external)
Boolean flag. Default: 0

### Radiation-Hydrodynamics Test 1 - Constant Fields (400)¶

Basic FLD radiation problem initializer, allowing setup of uniform fields throughout the computational domain, which are useful for testing radiation/material couplings. Test problem used for problem 4.2 in (Reynolds et al., “Self-consistent solution of cosmological radiation-hydrodynamics and chemical ionization,” JCP, 2009).
RadHydroVelocity (external)
Initialize velocity of ambient gas in the x,y,z directions. Default: 0 (all). Example RadHydroVelocity = 0.1 0.1 0.1
RadHydroChemistry (external)
Number of chemical species. 1 implies hydrogen only, 3 implies hydrogen and helium. Default: 1.
RadHydroModel (external)
Type of radiation/matter coupling: 1 implies a standard chemistry-dependent model, 4 implies an isothermal chemistry-dependent model, 10 implies a chemistry-independent model in thermodynamic equilibrium. Default: 1
RadHydroDensity (external)
Ambient density. Default: 10
RadHydroTemperature (external)
Ambient temperature. Default: 1
RadHydroIEnergy (external)
Ambient internal energy (replaces temperature, if specified). Default: -1
RadHydroRadiationEnergy (external)
RadHydroInitialFractionHII (external)
Initial fraction of ionized hydrogen (in relation to all hydrogen). Default: 0
RadHydroHFraction (external)
Initial fraction of hydrogen (in relation to the total density). Default: 1
RadHydroInitialFractionHeII (external)
Initial fraction of helium II (in relation to the total helium). Default: 0
RadHydroInitialFractionHeIII (external)
Initial fraction of helium III (in relation to the total helium). Default: 0

### Radiation-Hydrodynamics Test 2 - Streams (401)¶

Streaming radiation tests. The problem utilizes a uniform density and a constant opacity, setting one face of the domain to have a radiation energy density of 1. The radiation front propagates through the domain at the speed of light. The sharpness of the radiation front is determined by the spatial resolution. Test problem used for problem 4.1 in (Reynolds et al., “Self-consistent solution of cosmological radiation-hydrodynamics and chemical ionization,” JCP, 2009).
RadHydroDensity (external)
Ambient density. Default: 1.0
RadHydroRadEnergy (external)
RadStreamDim (external)
Dimension to test {0,1,2}. Default: 0
RadStreamDir (external)
Direction for streaming radiation. 0 for left to right. 1 for right to left. Default: 0

### Radiation-Hydrodynamics Test 3 - Pulse (402)¶

RadHydroDensity (external)
Ambient density. Default: 1.0
RadHydroRadEnergy (external)
RadPulseDim (external)
Dimension to test {0,1,2}. Default: 0

### Radiation-Hydrodynamics Test 4 - Grey Marshak Test (403)¶

Test problem used for problem 4.3 in (Reynolds et al., “Self-consistent solution of cosmological radiation-hydrodynamics and chemical ionization,” JCP, 2009).
RadHydroDensity (external)
Ambient density. Default: 1.0
RadHydroRadEnergy (external)
RadHydroGasEnergy (external)
Ambient gas energy. Default: 1.0
GreyMarshDir (external)
Propagation coordinate for Marshak problem. {0,1,2}. Default: 0

Test problem used for problem 4.4 in (Reynolds et al., “Self-consistent solution of cosmological radiation-hydrodynamics and chemical ionization,” JCP, 2009).
DensityConstant (external)
Ambient density. Default: 1.0
GasTempConstant (external)
Ambient gas temperature. Default: 1.0
RadTempConstant (external)
VelocityConstant (external)
Imposed fluid velocity. Default: 1.0
ShockDir (external)
Propagation coordinate for shock. {0,1,2}. Default: 0
CGSType (external)
1 = Astrophysical Setup Parameters; 2 = “lab” setup parameters, after Lowrie; Default: 1

### Radiation-Hydrodynamics Tests 10 and 11 - I-Front Tests (410/411)¶

Uniform density ionization front test problems. These tests are used to replicate the isothermal and temperature-dependent I-front tests 1 and 2 from (Iliev et al., “Cosmological Radiative Transfer Codes Comparison Project I: The Static Density Field Tests,” MNRAS, 2006). This test problem was used for problem 4.5 in (Reynolds et al., “Self-consistent solution of cosmological radiation-hydrodynamics and chemical ionization,” JCP, 2009).
RadHydroVelocity (external)
Initial velocity of ambient gas in the x,y,z directions. Default: 0 (all). Example RadHydroVelocity = 0.1 0.1 0.1
RadHydroChemistry (external)
Number of chemical species. 1 implies hydrogen only, 3 implies hydrogen and helium. Default: 1.
RadHydroModel (external)
Type of radiation/matter coupling: 1 implies a standard chemistry-dependent model, 4 implies an isothermal chemistry-dependent model. Default: 1
RadHydroDensity (external)
Ambient density. Default: 10
RadHydroTemperature (external)
Ambient temperature. Default: 1
RadHydroIEnergy (external)
Ambient internal energy (replaces temperature, if specified). Default: -1
RadHydroRadiationEnergy (external)
RadHydroInitialFractionHII (external)
Initial fraction of ionized hydrogen (in relation to all hydrogen). Default: 0
RadHydroHFraction (external)
Initial fraction of hydrogen (in relation to the total density). Default: 1
RadHydroInitialFractionHeII (external)
Initial fraction of helium II (in relation to the total helium). Default: 0
RadHydroInitialFractionHeIII (external)
Initial fraction of helium III (in relation to the total helium). Default: 0
NGammaDot (external)
Strength of ionization source, in number of photons per second. Default: 0
EtaRadius (external)
Radius of ionization source, in cells (0 implies a single-cell source). Default: 0
EtaCenter (external)
Location of ionization source, in scaled length units, in the x,y,z directions. Default: 0 (all). Example EtaCenter = 0.5 0.5 0.5

### Radiation-Hydrodynamics Test 12 - HI ionization of a clump (412)¶

Ionization of a hydrogen clump, used to investigate I-front trapping in a dense clump, and the formation of a shadow. This test replicates the test 3.4 from (Iliev et al., “Cosmological Radiative Transfer Codes Comparison Project I: The Static Density Field Tests,” MNRAS, 2006).
RadHydroVelocity (external)
Initial velocity of ambient gas in the x,y,z directions. Default: 0 (all). Example RadHydroVelocity = 0.1 0.1 0.1
RadHydroChemistry (external)
Number of chemical species. 1 implies hydrogen only, 3 implies hydrogen and helium. Default: 1.
RadHydroModel (external)
Type of radiation/matter coupling: 1 implies a standard chemistry-dependent model, 4 implies an isothermal chemistry-dependent model. Default: 1
RadHydroNumDensityIn (external)
Number density inside the clump. Default: 0.04
RadHydroNumDensityOut (external)
Number density outside the clump. Default: 0.0002
RadHydroTemperatureIn (external)
Temperature inside the clump. Default: 40
RadHydroTemperatureOut (external)
Temperature outside the clump. Default: 8000
RadHydroRadiationEnergy (external)
RadHydroInitialFractionHII (external)
Initial fraction of ionized hydrogen (in relation to all hydrogen). Default: 0
ClumpCenter (external)
Location of clump center, in cm, in the x,y,z directions. Default: 1.54285e22 1.018281e22 1.018281e22
ClumpRadius (external)
Radius of clump, in cm. Default: 2.46856e21
NGammaDot (external)
Strength of ionization source along left wall, in number of photons per second. Default: 0

### Radiation-Hydrodynamics Test 13 - HI ionization of a steep region (413)¶

Ionization of a steep density gradient, used to investigate HII region expansion along a 1/r^2 density profile. This test replicates the test 3.2 from (Iliev et al., “Cosmological Radiative Transfer Comparison Project II: The Radiation-Hydrodynamic Tests,” MNRAS, 2009).
RadHydroVelocity (external)
Initial velocity of ambient gas in the x,y,z directions. Default: 0 (all). Example RadHydroVelocity = 0.1 0.1 0.1
RadHydroChemistry (external)
Number of chemical species. 1 implies hydrogen only, 3 implies hydrogen and helium. Default: 1.
RadHydroModel (external)
Type of radiation/matter coupling: 1 implies a standard chemistry-dependent model, 4 implies an isothermal chemistry-dependent model. Default: 1
RadHydroNumDensity (external)
Number density inside the core of the dense region. Default: 3.2
RadHydroDensityRadius (external)
Radius of the dense region, in cm. Default: 2.8234155e+20
RadHydroTemperature (external)
Ambient temperature. Default: 100
RadHydroRadiationEnergy (external)
RadHydroInitialFractionHII (external)
Initial fraction of ionized hydrogen (in relation to all hydrogen). Default: 0
EtaCenter (external)
Center of the dense region (and ionization source), in cm, in the x,y,z directions. Default: 0 0 0
NGammaDot (external)
Strength of ionization source, in number of photons per second. Default: 0

### Radiation-Hydrodynamics Tests 14/15 - Cosmological HI ionization (414/415)¶

HI ionization in a uniform density field. This test problem was used for problems 4.6 and 4.8 in (Reynolds et al., “Self-consistent solution of cosmological radiation-hydrodynamics and chemical ionization,” JCP, 2009). Test 4.6 utilized a single ionization source (test 415), whereas 4.8 replicated the test to the center of every processor for performing weak-scaling tests (test 414).
RadHydroVelocity (external)
Initial velocity of ambient gas in the x,y,z directions. Default: 0 (all). Example RadHydroVelocity = 0.1 0.1 0.1
RadHydroChemistry (external)
Number of chemical species. 1 implies hydrogen only, 3 implies hydrogen and helium. Default: 1.
RadHydroModel (external)
Type of radiation/matter coupling: 1 implies a standard chemistry-dependent model, 4 implies an isothermal chemistry-dependent model. Default: 1
RadHydroTemperature (external)
Ambient temperature in K. Default: 10000
RadHydroRadiationEnergy (external)
Ambient radiation energy in erg/cm^3. Default: 1.0e-32
RadHydroInitialFractionHII (external)
Initial fraction of ionized hydrogen (in relation to all hydrogen). Default: 0
RadHydroOmegaBaryonNow (external)
Default: 0.2
NGammaDot (external)
Strength of ionization source, in number of photons per second. Default: 0
EtaRadius (external)
Radius of ionization source for test 415, in cells (0 implies a single-cell source). Default: 0
EtaCenter` (external)
Location of ionization source for test 415, in scaled length units, in the x,y,z directions. Default: 0 (all). Example EtaCenter = 0.5 0.5 0.5
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