Do BBFs contribute to inner magnetosphere dipolarizations: Concurrent Cluster and Double Star observations
Publication date: 11 November 2006
Authors: Takada, T. et al.
Journal: Geophysical Research Letters
Volume: 33
Issue: 21
Year: 2006
Copyright: American Geophysical Union
We examined the relationship between bursty bulk flow (BBF) events observed by Cluster between -19 RE < X < -12 RE and dipolarization events observed by Double Star TC1 between -13 RE < X < -6 RE. TC1 observed dipolarizations for ~33% of the cases when BBFs were observed by Cluster. During these dipolarization events the TC1 location was closer to the Cluster location and the local BZ at TC1 was smaller than during events where TC1 observed no clear dipolarization associated with BBFs at Cluster. This result suggests that (1) flow-associated activity dissipates within a limited spatial scale, 4-8 RE, and that (2) the initial magnetic topology in the inner magnetosphere can contribute strongly to fast flow penetration toward the Earth. The fact that there were no TC1 dipolarization events at X > -8 RE associated with BBFs at Cluster in our dataset suggests two possibilities: near-geosynchronous dipolarization needs another mechanism in addition to flux pile-up and braking, or during near-geosynchronous dipolarization the near-tail current sheet/plasma sheet is too thin to be observed by Cluster.
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