Modeling of the magnetosphere

Magnetospheric modeling is the art of deriving the configuration of the magnetosphere and representing its behavior. Two main levels exist: descriptive modeling which tries to represent the observed magnetic field B and perhaps the electric field E , and physical modeling which also includes plasma effects. Descriptive modeling must only satisfy Maxwell's equations, in particular ∇ · B = 0; physical modeling adds density ρ, pressure p etc. and must also satisfy conservation laws of magneto‐hydrodynamics (MHD). Discussed below are descriptive models and simple physical ones, up to the level of the magneto‐hydrostatic (MHS) approximation; full MHD simulations are covered in a companion report. In the MHS approximation the MHD momentum balance condition reduces to ∇p = j × B