HR: 09:25h
AN: SM21B-06    [Abstracts]
TI: Geosynchronous Response to Fast Plasma Flows in the Plasmasheet: Geotail-GOES Coordinated Observations
AU: Yamaguchi, R
EM: ruiy@math.kyushu-u.ac.jp
AF: Faculty of Mathematics, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581 Japan
AU: * Ohtani, S
EM: ohtani@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723-6099
AU: Mukai, T
EM: mukai@stp.isas.jp
AF: ISAS/JAXA, 3-1-1 Yoshinodai , Sagamihara, 229-8510 Japan
AB: In this study we examine how geosynchronous magnetic configuration changes in response to the first plasma flow in the plasmasheet. One idea of the substorm trigger (the pile-up/braking model) proposes that the fast earthward flow in the plasmasheet, which is created by near-Earth reconnection, reduces the tail current intensity as the flow is decelerated and changes the plasma distribution and magnetic field configuration in the near-Earth region. Although occasional observations of subsequent occurrence of a fast plasmasheet flow and geosynchronous dipolarization are consistent with (but are not necessarily the proof of) this idea, the generality of such observations still remains to be understood. In fact, for a pseudobreakup event we examined previously [Ohtani, Yamaguchi et al., GRL, doi:10.1029/2001GL013785, 2002], one GOES satellite observed that geosynchronous magnetic field actually became more stretched after Geotail observed a fast flow in the plasmasheet, even though the two spacecraft were aligned in the X direction and were separated by only 4 RE. A preliminary study of similar Geotail-GOES coordinated observations suggests that such events are not uncommon. We will address how often and under what conditions geosynchronous magnetic field dipolarizes following the fast plasmasheet flow.
DE: 2708 Current systems (2409)
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting