Modeling Inner Magnetospheric Electrodynamics

We describe a model of inner magnetospheric electrodynamics that couples the Rice Convection Model (RCM) to an equilibrium magnetic field model. The equilibrium model is a modified version of the Hesse-Birn [1993] magnetofriction code, adapted for use in the inner magnetosphere. Previous versions of the RCM, which used observation-based or theoretical magnetic field models, were flexible and convenient but lacked theoretical consistency. The coupled code uses the pressure distribution computed from the RCM to modify the magnetic field. We present results using the coupled code to model a substorm growth phase. Under conditions of steady sunward convection the computed inner plasma sheet magnetic field becomes increasingly stretched, the current-sheet thins, and a B z minimum forms at around x = -15 R E . In addition, region-l currents form poleward of the traditional region-2 currents found in the RCM. As the stress in the configuration continues to increase, the numerical method eventually fails. Nature presumably relieves the stress with a substorm expansion phase onset.

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