Current disruption during November 24, 1996, substorm

This study uses global magnetohydrodynamic (MHD) simulations driven by solar wind data along with Geotail, Interball, and IMP 8 observations of the magnetotail to investigate the dynamics of the near-Earth plasma sheet during a substorm that occurred on November 24, 1996. The MHD simulation shows that prior to the onset of the substorm, the magnitude of the current density decreases in a small region in the near-Earth plasma sheet. During and after the substorm onset this region of weak current becomes larger and more pronounced, expanding dawnward, duskward, upward, downward, and tailward. Part of the cross-tail current is redirected to the ionosphere via an earthward field-aligned current on the dawnside and a tailward return current on the duskside. The simulation showed that the field-aligned current was associated with velocity shear and flow vortices.