Global Simulation of the Response of Earth's Magnetosphere to the September 24, 1998, Interplanetary Shock


J Raeder, C T Russell, P Chi (all at: Institute of Geophysics and Planetary Physics, University of California, 405 Hilgard Ave, Los Angeles, CA 90095, USA, email:

H Singer (NOAA R/E/SE, Space Environment Center, 325 Broadway, Boulder CO 80303, USA)


A very strong interplanetary shock was observed by the Wind spacecraft on September 24, 1998, 2221 UT. The resulting sudden impulse (SI) was observed by several magnetospheric spacecraft, as well as by ground magnetometers. We study this event by using global magnetohydrodynamic simulation and examine the propagation of this disturbance through the magnetosphere. As expected, the interaction of the incident shock with Earth's bow shock leads to five new discontinuities: a fast shock that propagates through the magnetosheath, followed by a rotational discontinuity (RD), a tangential discontinuity (TD), another RD, and the new bowshock. These waves impinge on the magnetopause, from which then a fast wave propagates sunward and pushes the bow shock further out. Some fraction of the incident wave energy enters, and then propagates through the magnetosphere. The first signal reaching the tail plasma sheet at about 15 RE behind the Earth arrives about 80 seconds after the shock impinges on the magnetopause. At the Polar spacecraft the SI compresses the magnetosphere such the the magnetic footpoint of Polar changes within a few minutes by about 4 degrees in latitude and about 4 hours MLT. The latter result may be of significance when interpreting Polar plasma observations.