Statistical Analysis of Vortex-driven Field-aligned Currents

Abstract:

The substorm current wedge (SCW) is a current system that forms during substorms, and electrically couples the near-Earth plasma sheet in the nightside with the ionosphere via field-aligned currents. These field-aligned currents cause a multitude of phenomena during the course of a substorm, one of which is the substorm-related aurora. An understanding of the formation of this current system is of key importance for an understanding of the substorm phenomenon as a whole.

Large-scale plasma flow vortices in the near-Earth space environment have been shown to contribute to the field-aligned current of the SCW. While it has been argued that they do not provide the bulk current of the SCW, they are nevertheless an important “ignitor” of the SCW. Using multipoint measurements from the THEMIS fleet, we investigated the statistical relationship among spatial dimension, duration and associated current density of these plasma flow vortices during times of substorm.