HR: 1340h
AN: SM13B-1312    [Abstracts]
TI: Effects of plasma sheet condition on the evolution of shielding and the Harang reversal under weak convection: RCM simulations
AU: * GKIOULIDOU, M
EM: mgioul@atmos.ucla.edu
AF: DEPT. OF ATMOSPHERIC AND OCEANIC SCIENCES, UCLA, 405 HILGARD AVE., LOS ANGELES, CA 90095, United States
AU: LYONS, L R
EM: larry@atmos.ucla.edu
AF: DEPT. OF ATMOSPHERIC AND OCEANIC SCIENCES, UCLA, 405 HILGARD AVE., LOS ANGELES, CA 90095, United States
AU: WANG, C
EM: cat@atmos.ucla.edu
AF: DEPT. OF ATMOSPHERIC AND OCEANIC SCIENCES, UCLA, 405 HILGARD AVE., LOS ANGELES, CA 90095, United States
AU: WOLF, R A
EM: rawolf@rice.edu
AF: Physics and Astronomy Department, Rice University, 6100 Main Street, Houston, TX 77005, United States
AB: Shielding of the convection electric field and the Harang reversal associated with the region 2 field-aligned current system are fundamental manifestations of the large-scale plasma transport within the tail plasma sheet and the electrodynamic coupling of this transport to the ionosphere. However, how their formation and evolution is affected by the plasma sheet density and temperature is not well understood. We have used the RCM with Tsyganenko 96 magnetic field model to investigate this effect of plasma sheet conditions under weak convection. We have found that the existence of an overlap in local time of Region 2 upward and downward field aligned currents is necessary for the formation of the Harang reversal. The downward field aligned current in this overlap region is associated with electrons and low energy ions, while the upward field aligned current is associated with high-energy ions. Higher plasma sheet pressure can cause quicker shielding of the penetration electric field. If the time scale of the shielding is much shorter than the drift time scale of the low energy particles, these low energy particles cannot penetrate earthward enough to cause the overlap, thus preventing formation of the Harang reversal. Under the same plasma sheet pressure, higher auroral conductance can result in slower shielding. Higher plasma temperature enhances the upward field-aligned currents in the overlap region, therefore leading to a stronger Harang reversal. Currently we are running the simulation under different strengths of convection and with more realistic MLT dependent boundary conditions based on the Geotail observations.
DE: 2463 Plasma convection (2760)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting