HR: 1340h
AN: SM13B-1210    [Abstracts]
TI: Geotail Observations of Different Energy Plasma Sheet Ions Near the Nightside Magnetopause: Their Spatial Variations and Dependence on the Solar Wind Parameters
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: 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
AB: To understand the formation of the nightside low-latitude boundary layer and its role as a particle source to the inner plasma sheet and magnetosphere, we investigated the Geotail fluxes of plasma sheet ions (plasma beta $>$ 1, temperature $>$ 0.1 keV, and Vx $> -$100 km/s) averaged over three different energy ranges (low: 0.1--1 keV, intermediate: 1--10 keV, and high: 10--39 keV) in the region of X = 0 to $-$30 R$_E$ and within 2 R$_E$ inside the magnetopause (70 dusk side and 45 dawn side magnetopause crossings defined by a sharp gradient in Vx). Their dependence on the solar wind data obtained from WIND were also investigated. The solar wind data were averaged over different lengths of hours (from 0.5 to 6 hours) prior to the estimated impact time. On both the dawn and dusk flanks, the low and intermediate energy fluxes are found to be independent of X while the high energy fluxes increase with decreasing $|$X$|$. There is no significant dawn-dusk difference on the magnitudes of the fluxes for both the low and intermediate energy ions, but the magnitude range for the high energy fluxes is seen to be much wider on the dawn flank than on the dusk flank. Only the low energy fluxes on the dawn flank are found to vary with the distance from the magnetopause, with higher flux at smaller distance. On the dawn flank, the low and intermediate energy fluxes during strongly ($|$B$| >$ 5 nT) positive IMF Bz are clearly higher than the fluxes observed during strongly negative IMF Bz while the high energy fluxes have the opposite dependence. This dependence become clearer when the fluxes are correlated with longer periods of IMF data. On the dusk flank, there are not enough events for strongly negative IMF Bz to reveal clear IMF Bz dependence. The low and intermediate energy fluxes are seen to increase (decrease) with solar wind density (solar wind speed), while the high energy fluxes are seen to increase with increasing solar wind speed but have no dependence on solar wind density. No obvious difference is seen when correlated with longer periods of solar wind moment data. That very different spatial and solar wind condition dependence observed in the low and high energy ions suggests their access to the flanks and their variations are controlled by different processes.
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2744 Magnetotail
DE: 2748 Magnetotail boundary layers
DE: 2764 Plasma sheet
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting