Simulation of the March 9, 1995, substorm: Auroral brightening and the onset of lobe reconnection

A global MHD simulation of an isolated substorm that occurred on March 9, 1995 is presented. The simulation, driven with solar wind data provided by the Wind satellite, reproduced to a surprising degree the evolution of substorm activity. The onset of the expansion phase was coincident with the penetration of an electric field spike into the nearEarth region. This impulse launched a tailward propagating signal (rarefaction wave) that enhanced reconnection in the mid tail. Substorm intensification was correlated with th'e enhancement of the reconnection rate at the preexisting reconnection region located at 30 Re. The importance of the electric field spike in correlating ionospheric and magnetospheric aspects of the substorm is emphasized.