IWF : Dipolarization near the flow braking region



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Dipolarization near the flow braking region

Dipolarization, i.e. enhancement in Bz, has been known as signature of substorm onset as well as signatures of accompanied plasma sheet fast flows, which can be observed at near-Earth as well as midtail region. A unique constellation of Cluster near the flow braking region (around 10 RE) allowed to resolve for the first time two different types of dipolarization: dipolarizytion due to Earthward moving rapid flux transport (D1) and dipolarization due to flux lipeup (D2) indicated in the figure. Cluster was in a multi-scale constellation, in which measurement of both the large scale (10000)km development of the dipolarization front and the high-resolution (50 km) current density could be performed.

It is found that the current sheet disturbance is induced by the first dipolarization pulses (D1) accompanied by the plasma flow, but the resulting types of disturbances depend on the configuration of the current sheet. That is, when the ambient current sheet is thin (Event A), dipolarization pulse caused further thinning with a kinkmode-like oscillation. When teh ambient field is more dipolar as in event B and C, the dipolarizatiopn is accompanied by hte disturbances in small scale vertical current sheet and signature of flow braking.

(from Nakamura et al., Ann. Geophys., 27, 1743-1754, 2009)

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Last update: 01/26/10