HR: 09:00h
AN: SM41A-05    [Abstracts]
TI: A Statistical Examination of the Relation between Substorm Onsets and Magnetic and Plasma Changes in the Tail
AU: Hsu, T
EM: thsu@igpp.ucla.edu
AF: IGPP/UCLA, 405 Hilgard Ave. , Los Angeles, CA 90095, United States
AU: * McPherron, R
EM: rmcpherr@igpp.ucla.edu
AF: IGPP/UCLA, 405 Hilgard Ave. , Los Angeles, CA 90095, United States
AU: Borovsky, J
EM: jborovsky@lanl.gov
AF: Los Alamos National Laboratory, Los Alamos, Los Alamos, NM 87545, United States
AB: Substorms are so complex that many issues related to them remain very controversial. Many models have been proposed to explain substorm activity. These models can be broadly classified into two categories depending on the cause of the expansion onset. The first invokes processes in the near-Earth region (|X| < 15 Re) such as current sheet disruption, instability triggered by reduction of interplanetary electric field, or some feed back instabilities near the ionosphere. The other invokes mid-tail magnetic reconnection beyond |X| ~ 15 Re as a source of plasma flowing earthward. Deceleration of this earthward flowing plasma and pileup of magnetic flux close to the Earth is then the cause of near-Earth disturbances. A possible way to distinguish the cause of substorm expansion onset is to examine the relative timing of magnetotail disturbances. If the near-Earth region is the source region of substorm onset, a disturbance should be first observed in the near-Earth region and later in the midtail. Similarly, the opposite time delay should be observed if the mid-tail reconnection is the source of substorm expansion onset. In this study, we have identified several candidate events with chance conjunctions of GOES, GEOTAIL, POLAR, and Cluster. Data from auroral imagers, ground magnetometers, Pi 2 pulsation detectors, and synchronous particle detectors will be used to establish accurate onset times. IMF observation will be accurately time propagated by Weimer et al [2002] algorithm. The starting time of near and mid-tail disturbance from these multi- satellite observations will be compared with substorm onset time to establish a relative timing pattern during substorms.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2784 Solar wind/magnetosphere interactions
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly