HR: 1340h
AN: SM33A-1106    [Abstracts]
TI: Variations of Magnetic Fields at Geosynchronous Orbit: Relative to the Location of Substorm Expansion
AU: * Shue, J
EM: jhshue@jupiter.ss.ncu.edu.tw
AF: Institute of Space Science, National Central University, Jhongli, 32001, Taiwan
AU: Wu, K
EM: khwu@jupiter.ss.ncu.edu.tw
AF: Institute of Space Science, National Central University, Jhongli, 32001, Taiwan
AU: Liou, K
EM: Kan.Liou@jhuapl.edu
AF: Applied Physics Laboratory, The Johns Hopkins University, Laurel, 20723, United States
AB: The magnetospheric configuration is tail-like when the interplanetary magnetic field is southward. The magnetosphere turns into a dipole-like configuration during a substorm expansion. The dipolarization region can be identified from an increase in the Z component of the magnetic fields at geosynchronous orbit. Variations of the magnetic fields at geosynchronous orbit during substorms were studied in terms of magnetic local time. However, their magnetic variations in terms of the relative distance of the foot point of a satellite to the location of a substorm expansion have not been studied. In this study, we calculate inclination angles that indicate the stretching or dipolarization level of the magnetic field lines using GOES 8 and 9 magnetic fields data for a list of substorm events identified from Polar Ultraviolet Imager auroral images. Magnetic variations for all the events are organized in averages with epoch zero to the substorm expansion onset under the various relative distances. These results show that the region where the inclination angle reaches its smallest value (or the largest stretching of the field lines) is found at one hour of local time west of the onset location before the onset. Also, the region where has the largest dipolarization (or the largest increase in the inclination angle during the substorm expansion) is found at one hour of local time east of the onset location after the onset. We will discuss the implication of these results in the presentation.
DE: 2704 Auroral phenomena (2407)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2730 Magnetosphere: inner
DE: 2740 Magnetospheric configuration and dynamics
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting