Gibson & Low 1998 model of CME (or magetostatic solution).

Note this model (in its magnetostatic form, phiss=1, alpha=0) represents an analytic, three-dimensional equilibrium solution.  However, it is intrinsically not force-free with a polytropic relationship between density and pressure.

For this reason we provide an option for "Bonly", which, if set, forces an isothermal solution and a hydrostatic background (the spheromak portion of the field may be a fraction of the surrounding background).  This will not be in equilibrium, but allows an investigation of the magnetic structure with realistic density/temperature, for example for the Comp Stokes polarimetric observabes.

Alternatively, the Lites-Low model may be used.  This model is force-free both in the spheromak and surrounding open field regions.  This solution will be in equilibrium except at the interface between spheromak and open field solution.