Journal of geomagnetism and geoelectricity
Online ISSN : 2185-5765
Print ISSN : 0022-1392
ISSN-L : 0022-1392
Low Altitude Signatures of the Plasma Sheet: Model Predictions of Local Time Dependence
Karen L. HirschHarlan E. SpenceTerrance G. Onsager
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1996 Volume 48 Issue 5-6 Pages 887-895


We combine two theoretical models of plasma sheet particle transport to trace plasma sheet particles from the nightside magnetospheric equatorial plane to low altitudes. We predict that the low-altitude signature of the plasma sheet is manifestly different at different local times. The Guiding Center Transport Model (GCTM) (Onsager et al., 1993) uses a given particle energy, position, and an assumed magnetic and electric field to trace the low-altitude particle's trajectory to the plasma sheet. The Finite Tail Width Convection Model (FTWCM) (Spence and Kivelson, 1993) uses two Maxwellian plasma sources, one downtail and one on the dawnside boundary layer, to generate distribution functions across the tail plasma sheet. Using Liouville's theorem, the distribution functions at the equatorial level are projected to low altitudes. When this signature of the plasma sheet is projected to low altitudes near the Earth, the spatial variation in the equatorial plasma properties produce a latitudinal variation in the isoflux contours. Isoflux contours at high latitudes at dawn extend to lower latitudes at dusk, reflecting a larger plasma sheet plasma pressure at dusk than at dawn. This prediction is based solely on a projection of spatial variations in equatorial plasma properties.

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