HR: 1330h
AN: SM32B-1155    [PDF]
TI: Penetration Electric Fields and Magnetospheric Convection During the April, 2002 Geomagnetic Storms
AU: * Anderson, P C
EM: phillip.c.anderson@aero.org
AF: The Aerospace Corporation, Box 92957 M2/260, los Angeles, CA 90009 United States
AB: We analyze the magnetospheric electric field strength and penetration electric fields during the series of geomagnetic storms in April, 2002 using measurements of the ion drifts in the ionosphere by the DMSP spacecraft. The cross-polar-cap potential drop ($\Psi_{PC}$) is seen to begin increasing at the beginning of the storm growth phases, maximizing near the beginning of the recovery phases, and exceeding 180 kV for three of the storms. The subauroral potential drop ($\Psi_{SA}$) in the evening sector exceeds 60 kV during three of the storms and can be a substantial fraction of $\Psi_{PC}$ - up to 78%. The largest $\Psi_{SA}$ values are seen in the dusk sector and diminish with increasing MLT. This is attributed to the greater separation between in the dusk sector between the inner edge of the electron and ion plasmasheets where the Region 2 field-aligned currents (FAC) flow into a region of low subauroral ionospheric conductivity, driving large electric fields. There is a good correlation of $\Psi_{PC}$ and $\Psi_{SA}$ with both Dst and AE - greater than 0.7. The best correlation with both potential drops occurs with no time delay for AE and with a 45 minute delay for Dst with $\Psi_{PC}$. However the best correlation for Dst with $\Psi_{SA}$ occurs well into the recovery phase with a time delay of ~4 hours. This is attributed to the movement of the inner edge of the electron plasmasheet/aurora to higher latitudes exposing a broader region of low ionospheric conductivity to the Region 2 FAC still being maintained by the equatorial ion pressure gradients as the ring current/ion plasmasheet decays.
DE: 2712 Electric fields (2411)
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2760 Plasma convection
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting