HR: 0800h
AN: SM31B-02    [Abstracts]
TI: Cross-Tail Electric Field Magnitude Derived From Plasmaspheric Alfven Layer Motions
AU: * Larsen, B A
EM: larsen@ssel.montana.edu
AF: Space Science and Engineering Laboratory Department of Physics Montana State University, 264 EPS Bldg, Bozeman, MT 59717, United States
AU: Klumpar, D M
EM: klump@physics.montana.edu
AF: Space Science and Engineering Laboratory Department of Physics Montana State University, 264 EPS Bldg, Bozeman, MT 59717, United States
AU: Gurgiolo, C
EM: chris@gurgiolo.com
AF: Bitterroot Basic Research, 837 Westside Road, Hamilton, MT 59840-9369, United States
AB: The plasmasphere is a highly dynamic region of considerable importance as an energy conduit in magnetosphere-ionosphere coupling and for its role in the modulation of the ring current and radiation belts. A complete explanation of the mechanism(s) responsible for the morphology of the plasmasphere, especially the morphology of small scale features, has yet to be found. The macro-dynamics are driven by the convective plasmasphere model, which is based on the superposition of the cross-tail convection electric field and the Earth's corotation electric field. The general plasmasphere shape is formed and modulated through E-cross-B drift of the local plasma. In the convective plasmasphere model, the steady state plasmapause is identified as the location of the last closed streamline, known at the plasmaspheric Alfven layer. Comparisons of the response times of plasmapause motion to response times of changes in the intensity of the cross-tail electric field guarantee that the plasmapause and Alfven layer only coincide during extended quiet periods. Variations in response time allow for observations of the Alfven layer position interior to the plasmapause which provides a means to compute the convection electric field by tracking its location in IMAGE-EUV plasmaspheric images. This study presents the EUV derived convection electric field for two storm-time events, 8 April 2001 and 17 April 2001, over a range of 0.25 to 0.5 mV/m. The fit is excellent between the EUV derived convection field and the convection field as derived from a Weimer model for the polar cap potential based on the IMF magnitude, clock angle, and solar wind velocity.
DE: 2712 Electric fields (2411)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2768 Plasmasphere
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly