Dynamics of the current sheet in Earth's magnetotail by the impact of an interplanetary shock

Abstract:

Earth’s magnetosphere is strongly disturbed by the impact of an interplanetary shock. In this study we report the dynamics of the current sheet in the near-Earth magnetotail at ~-17 R_E observed by the Cluster spacecraft when an interplanetary shock impacted Earth’s magnetosphere. Right after the storm sudden commencement (SSC) induced by the impact the current density, estimated by the curlometer technique using the Cluster constellation, strongly enhanced, which represents the thinning of the current sheet. Along with the thinning the density and temperature of the plasmas significantly increased and earthward bursty flows occurred. However, there was no signature of dipolarization of the magnetic field. About 20 minutes later Cluster entered a region with very small current density while maintaining the enhanced density and temperature of the plasmas. Then, about an hour after the SSC strong fluctuations of the current sheet with dipolarization started, which was associated with sudden drop of the AL index on the ground. This observation implies that the compression of the magnetosphere associated with the SSC almost simultaneously occurs over large regions from the inner magnetosphere to the near-Earth magnetotail. However, the activity associated with substorms may occur with some time delay.