1. A computerized method of accelerating calculation of L* in accordance with physics-based model of conditions in a magnetosphere comprising: defining a surrogate model to be a surrogate for a physics-based model of L* for magnetic belts based on formula L*=(2πμ 0 )/(ΦR E ) providing surrogate model computer instructions and surrogate model data; training the surrogate model to be a surrogate for the physics-based model of L* for magnetic belts based on the formula L*=(2πμ 0 )/(ΦR E ), wherein the physics-based model uses a plurality of physics-based model parameters, further comprising: providing physics data based on the physics-based model parameters; providing spatial data representing spatial coordinates for the location where L* is to be calculated; providing surrogate models including sets of data for the physics-based model for each of a plurality of pitch angles; selecting from the plurality of surrogate models at least one surrogate model set of data and instructions that calculate a closed drift shell for the physics-based model parameters and the spatial coordinates; and calculating L* by providing the physics-based model parameters and the spatial coordinates to the selected surrogate models that calculate a closed drift shell; and processing the trained surrogate model with a computer processor to accelerate the calculation of L* over a physics-based model.