The stability of a plasma is an important consideration in the study of plasma physics. When a system containing a plasma is at equilibrium, it is possible for certain parts of the plasma to be disturbed by small perturbative forces acting on it. The stability of the system determines if the perturbations will grow, oscillate, or be damped out. In many cases, a plasma can be treated as a fluid and its stability analyzed with magnetohydrodynamics (MHD). MHD theory is the simplest representation of a plasma, so MHD stability is a necessity for stable devices to be used for nuclear fusion, specifically magnetic fusion energy. There are, however, other types of instabilities, such as velocity-space instabilities in magnetic mirrors and systems with beams. There are also rare cases of systems, e.g. the field-reversed configuration, predicted by MHD to be unstable, but which are observed to be stable, probably due to kinetic effects. Plasma instabilities Plasma instabilities can be divided into two general groups: hydrodynamic instabilities kinetic instabilities. Plasma instabilities are also categorised into different modes (e.g. with reference to a particle beam): List of plasma instabilities Buneman instability, Farley–Buneman instability, Jeans–Buneman instability, Relativistic Buneman instability, Cherenkov instability, Coalescence instability, Non-linear coalescence instability Chute instability, Collapse instability, Cyclotron instabilities, including: Alfven cyclotron instability Cyclotron maser instability, Electron cyclotron instability Electrostatic ion cyclotron Instability Ion cyclotron instability Magnetoacoustic cyclotron instability Proton cyclotron instability Non-resonant beam-type cyclotron instability Relativistic ion cyclotron instability Whistler cyclotron instability Diocotron instability, (similar to the Kelvin-Helmholtz fluid instability). Disruptive instability (in tokamaks) Double emission instability, Edge-localized modes, Explosive instability (or Ballooning instability), Double plasma resonance instability, Drift instability (a.k.a. drift-wave instability, or universal instability) Lower hybrid (drift) instability (in the Critical ionization velocity mechanism) Magnetic drift instability, Slow Drift Instability Electrothermal instability Fan instability, Firehose instability (a.k.a. hose instability), not to be confused with the similarly named Firehose instability in galactic dynamics Fish instability, Free electron maser instability, Gyrotron instability, Helical (Helix) instability, Jeans instability, Magnetorotational instability (in accretion disks) Magnetothermal instability (Laser-plasmas), Modulational instability Non-Abelian instability, Pair instability (in supernovae) Parker instability (magnetic buoyancy instability), Peratt instability (stacked toroids) Pinch instability (a.k.a. Bennett pinch instability), Sausage instability (m=0) Kink instability (m=1) Helical kink instability (a.k.a. helical instability) Rayleigh–Taylor instability (RTI, a.k.a. gravitational instability) Interchange instability (a.k.a. flute instability), Rotating instability, Tearing mode instability (or resistive tearing instability) Two-stream instability (a.k.a. beam-plasma instability, counter-streaming instability) Beam acoustic instability