HR: 11:40h
AN: SM22A-06    [Abstracts]
TI: Multi-Spacecraft and ground-based observations of substorm activations¡GTwo case studies
AU: * Cao, X
EM: octorcx@agu.org
AF: Institute of Space Physics and Applied Technology, Peking University, Room N419, Physics Building, Peking University, No 5 Yiheyuan Road, Haidian District, Beijing, 100871, China
AU: Pu, Z
EM: zypu@pku.edu.cn
AF: Institute of Space Physics and Applied Technology, Peking University, Room N419, Physics Building, Peking University, No 5 Yiheyuan Road, Haidian District, Beijing, 100871, China
AU: Zhang, H
EM: hui@pku.edu.cn
AF: Institute of Space Physics and Applied Technology, Peking University, Room N419, Physics Building, Peking University, No 5 Yiheyuan Road, Haidian District, Beijing, 100871, China
AB: Two case studies are performed based on Double Star TC1¡ACluster¡APolar¡AIMAGE¡ALANL geostationary satellites and ground-based Pi2 measurements. In both events an earthward flow is measured by Cluster ~8-10 minutes ahead of aurora breakup. About 1 to 3 minutes prior to the breakup, TC1 may or may not observe the flux pileup-related magnetic field compression. A couple of minutes after the breakup, either TC1 first detects plasmasheet expansion and then LANL satellites near the midnight measure energetic electron injections at the geostationary orbit, or vise versus. About 20 minutes (or more) later, Cluster and Polar observe plasmasheet expansion successively. It is seen that in addition to a sudden decrease of Bx, simultaneous jump of Bz, and reversal of By, plasmasheet expansion is also characterized by a sharp increase of temperature of thermal ions and electrons, with a higher value in T// than TƒÎ. A short-lived earthward flow produced by substorm acceleration commonly appears as well, which is distinguishable from the flows ahead of onsets. Substorm expansion onset is shown to begin in the near-Earth tail around X~ -(8-9) RE. The tailward progression speed of plasmasheet expansion and the earthward propagation speed of substorm injection are estimated ~ 82 km/s and ~25 km/s, respectively. Poleward expansion of auroral bulges in the ionosphere and tailward progression of substorm expansion (SCW) in the magnetotail are shown to be closely related. An initial dipolarization in the near-Earth may eventually evolve to enable disruption of the cross-tail current in a wide range of the magnetotail.
DE: 2744 Magnetotail
DE: 2788 Magnetic storms and substorms (7954)
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting