Self-Consistent Modeling of Storm-Time Subauroral Electric Fields

Details Self-Consistent Modeling of Storm-Time Subauroral Electric Fields Self-Consistent Modeling of Storm-Time Subauroral Electric Fields

Dec 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsm22a0571s&link_type=abstract

American Geophysical Union, Fall Meeting 2002, abstract #SM22A-0571

Physics

2411 Electric Fields (2712), 2730 Magnetosphere: Inner, 2736 Magnetosphere/Ionosphere Interactions, 2753 Numerical Modeling, 2778 Ring Current

Scientific paper

Highly dynamic inner magnetospheric electric fields are associated with pressure gradients near the inner edge of the plasma sheet and with the closure of field-aligned region-2 (Birkeland) currents through the auroral and subauroral ionosphere. During geomagnetic storms, the inner edge of the ion plasma sheet, which carries the bulk of the plasma-sheet pressure, is brought closer to the Earth in the dusk-midnight local time sector than the electron population whose precipitation into the ionosphere provides most of the enhanced conductance in the auroral ionosphere. The result is a SubAuroral Polarization Stream (SAPS), a band of fast westward convection located equatorward of the diffuse aurora. This picture of the SAPS phenomenon has been consistently predicted by the Rice Convection Model (RCM), a numerical model of the coupled ionosphere-magnetosphere system. In this paper, we present results of self-consistent RCM simulations of inner magnetospheric electric fields, for several geomagnetic storms, to show that: (1) The dynamics of a SAPS is controlled by the strength of the overall plasma sheet convection. (2) While field-aligned currents associated with pressure gradients in the asymmetric ring current play an integral role in the dynamics of the inner magnetosphere during storms, self-consistent calculations show that the ring current itself responds quickly to changes in the overall strength of magnetospheric convection. (3) The RCM-based picture is consistent with images obtained from the HENA instrument on board the IMAGE spacecraft. In particular, both the RCM and the HENA images indicate formation of the asymmetric ring current in the main phase; however, the ring current pressure quickly becomes nearly symmetric (in local time) if the convection strength suddenly decreases.

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