HR: 0800h
AN: SM31B-1226    [Abstracts]
TI: Reoccurrence Substorms and Their Responses to IMF Variance
AU: * Hong, M
EM: mhhong@physics.auburn.edu
AF: Auburn University, Department of Physics, Auburn, AL 36849 United States
AU: * Hong, M
EM: mhhong@physics.auburn.edu
AF: Institute of Geology and Geophysics, Institute of Geology and Geophysics, Beijing, 100029 China
AB: The critical problem in magnetospheric substorm study is the cause of substorm onset. We examined the reoccurrent substorms which well defined with energetic particle data and magnetic data in geosynchronous ground geomagnetic data. 5 events are analyzed. During these events, nearly simultaneous particle flux enhancements and magnetic field variances occurred at geosynchronous, coincided well with the geomagnetic field H-component dramatically decreasing in high latitude nightside regions, which are defined as substorm signatures. With examining IMF data, 4 events occurred when the IMF stayed sustaining southward, but disturbed, One event occurred during relative stable southward IMF. All these events occurred during magnetic storm main phase, and ended at early stage of recovery phase. We find that the reoccurrence substorm onsets are associated with relative change in IMF, especially IMF Bz northward turning. The periods of substorm reoccurrence are 2-3 hour, which dependent on the variances in IMF. Based on present study, we suggest that the necessary condition for substorm onset is enough energy accumulated in magnetotail, leading to an instable magnetotail, external variances in IMF trigger the substorm onset.
DE: 2731 Magnetosphere--outer
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting