Modeling Extreme Compression of the Magnetosphere: Results from a Global MHD Simulation of the May 4, 1998 Event

Abstract

This paper reports results from a global magnetohydrodynamic (MHD) simulation of the extreme compression of the magnetosphere that occurred on May 4, 1998. Simultaneous Wind spacecraft measurements of solar wind ions and the interplanetary magnetic field (IMF) upstream of the Earth were used as driving input for the MHD simulation. After assessing the validity of the model by comparing time series from the simulation with Geotail and Polar measurements, we examined the interaction of the leading edge of the solar disturbance with the magnetosphere. The simulation shows that the initial interaction of the interplanetary shock with the Earth bow shock produced a sunward motion of the resultant bow shock and that the transmitted shock wave launched a fast compressional wave at the magnetospheric boundary. We conclude the paper by examining the magnetotail's reaction to a sustained period of strong dynamic pressure. The simulation results suggest that the magnetotail can attain highly organized states during which large-scale flows are more laminar than expected.