Computing magnetospheric force equilibria

Abstract

We describe a method to compute three-dimensional force equilibria in the Earth's magnetosphere. The method is embodied in a code called the MagnetoFriction code which solves a set of ideal magnetohydrodynamic (MHD) equations that are modified to include a factional dissipation term in the momentum equation. The friction takes the form of a force which is directed against the fluid motion and is therefore an energy sink. This allows the system to settle into a minimum energy equilibrium. A nonuniform cartesian grid is used along with initial conditions supplied by empirical magnetic field and pressure models. These initial conditions do not, in general, satisfy the force balance condition J→ × B→ = ∇p, and the code must iterate until approximate force balance is achieved. Pressure and magnetic field solutions are presented for several different configurations of the magnetosphere. Copyright 2003 by the American Geophysical Union.