GEM: A Modular Model of the Storm-Time Magnetosphere

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The proposed work would generalize the Rice Field Model to include the effects of polar-cap potential saturation and asymmetric ring currents, both of which are especially important during magnetic storm intervals when the magnetosphere is driven hard by the solar wind. Both of these generalizations require the incorporation of Birkeland (magnetic-field-aligned) currents and their magnetic effects. The Rice Field Model is a modular model of the global magnetic- and electric-field configuration of the Earth's magnetosphere that presently includes the geodipole, the confining effect of magnetopause (Chapman-Ferraro) currents, cross-tail currents, a symmetric ring current, and an "interconnection" field that links the interplanetary magnetic field to the geodipole. The new features to be added include the three global Birkeland-current systems, Region 1 (R1), Region 2 (R2), and Cusp Region (CR), along with their closure currents on the magnetopause (R1 and CR) and in the inner magnetosphere (R2). The R1 and CR currents will be specified from the divergence of the ionospheric Pedersen current that is driven by the electric field mapped inward from the solar wind. The R2 current will be specified from the divergence of an asymmetric inner-magnetospheric ring current. Calculating the magnetic effects of these Birkeland current systems will be done with a novel approach to approximating the Biot-Savart integral. The calculation will be done in iterative steps such that the Birkeland currents remain parallel to the resultant magnetic field. These improvements will make the model applicable to large magnetic storms The improved model will contribute to our understanding of the structure and dynamics of the storm-time magnetosphere. The proposed model will be applicable to a Geospace General Circulation Model (GGCM), which will be useful for space weather nowcasting and forecasting. The project provides educational impacts by supporting a graduate student and a postdoctoral student.