Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1777307 | Journal of Atmospheric and Solar-Terrestrial Physics | 2010 | 10 Pages |
Abstract
We examined the temporal variations of the geomagnetic field and energetic ions at geosynchronous altitudes associated with substorms during the nighttime using a superposed epoch analysis timed by Pi2 onset. We focused on the first 10Â min intervals of Pi2 onset and on subsequent intervals to study the substorm expansion. We conclude that the first 10Â min interval of Pi2 onset is a transitional state of the substorm dominated by MHD processes associated with earthward flow and its bifurcation. Intervals of field line variations following the first 10Â min were well organized by dipolarization (substorm current wedge) due to the reduced cross-tail current. We also show that energetic ion regions localized in the local time sector from 2000 to 0000Â LT in the first 10Â min intervals of Pi2 onset expanded to the post-midnight sector, reaching 0400Â LT within 20Â min after Pi2 onset. We conclude that the expansion of the energetic plasma regions can be attributed to the inflation of the inner magnetosphere during dipolarization.
Keywords
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Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
O. Saka, K. Hayashi, M. Thomsen,