HR: 0800h
AN: SM31A-08    [Abstracts]
TI: Magnetic field Distortions and Energetic Particle Enhancements in the Southern Dawnside High-Latitude Region During a Geomagnetic Storm Period
AU: * Chen, J
EM: jschen@bu.edu
AF: Boston University, Center for Space Physics, 725 Commonwealth Avenue, Boston, MA 02215, United States
AU: Fritz, T A
EM: fritz@bu.edu
AF: Boston University, Center for Space Physics, 725 Commonwealth Avenue, Boston, MA 02215, United States
AB: The magnetic field distortions are observed by CLUSTER with orders of magnitude enhancements of the energetic (30 keV - 1 MeV) charged particles (electrons and ions) in the southern high-latitude region around 6 MLT for about two hours, from 15:10 UT to 17:20 UT, on May 4, 2006 when a geomagnetic storm (Dst=-62 nT) was detected. During this period, the IMF Bz was pointing northward, and the IMF By was pointing duskward for most of the time. The northward IMF component could reconnect with the geomagnetic field at the southern polar cap region, while the duskward IMF component might reconnect with the geomagnetic field in the dawnside high-latitude region in the southern hemisphere. The measured local magnetic field shows diamagnetic cavities with large fluctuations. The cavities and particles are very similar to those called cusp energetic particle (CEP) events that were previously found by POLAR in the high-altitude dayside cusp region. The geomagnetic storm started at about 11 UT on 5/4/06. The AE index increased from about 200 nT at 12:10 UT to about 1000 nT at 13:50 UT and decreased to less than 200 nT at 16 UT on that day. The geosynchronous particle data indicate that there were two energetic particle injections observed near midnight at 12:10 UT and 13:50 UT. These observations suggest a global effect in the magnetosphere drived by the external solar wind/IMF conditions. A preliminary analysis suggests that the energetic particle injection near midnight are due to substorms and the enhancements of the energetic particles in the southern dawnside high-latitude region are due to some unknown energization mechanisms. These are two different processes even if they have the same external drivers. The relations between the field distortions and the energetic particle populations and the relations between the storms/substorms and the CEP-like events in the southern dawnside high-latitude region will be discussed.
DE: 2706 Cusp
DE: 2720 Energetic particles: trapped
DE: 2731 Magnetosphere: outer
DE: 2740 Magnetospheric configuration and dynamics
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly