IWF : Dipolarization and currents



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Dipolarization and currents

Magnetic field dipolarization is a suden change of the magnetic field structure, from a stretched configuration (tail-like) toward a dipolar configuration, and is observed associated with fast plasma flows. Development of flux tubes associated with dipolarization was successfully monitored simultaneously by Cluster, located near the magnetotail current sheet at 16 RE, and by DSP TC1, located at 7 RE in the lobe. A dipolarization was observed by Cluster accompanied by magnetic field variations that can be interpreted due to field-aligned current system, which was supported by the electron observations from the PEACE instrument. These field aligned currents were simultanously observed by DSP TC1.

The figure illustrates the summary of the observation by Cluster and TC1. After the dipolarization, hte magnetic field returned to be tail-like again, with the plasma flow and magnetic flux transport going tailward. This means, that there was local and remote sensing of this imward-outward motion of the magnetic flux and plasma flow in the magnetotail. At TC1, which was on field lines associated with the dipolarization, there was no evidence of magnetic field dipolarization. However, the plasma flow at TC1 showed strong correlation with the plasma flow and flux transport measured by Cluster. It is therefore proposed that the inward-outward motion of the plasma and field at Cluster work as a piston, influencing the plasma motion at hte location of TC1.

(from Volwerk et al, J. Geophys. Res., 113, A08S90, doi:10.1029/2007JA012729, 2008)

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Last update: 01/26/10