SM32C-03 1400h

POLAR Magnetosheath Observations on May 4, 1998

J. U. Kozyra1 (1-734-647-3550;

P. Song1(1-734-764-8327;; M. 0. Chandler2; T. E. Moore3; C. T. Russell4; S. S. Stahara5;
J. R. Spreiter5; J.-H. Shue6

1Space Physics Research Lab, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109-2143, United States

2Space Sciences Laboratory, NASA Mail Code ES83, NASA MarshO Space Flight Center, Huntsville, AL 35812, United States

3Interplanetary Physics, Code 692, Bldg.2-Rm 138, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States

4Institute of Geophysics and Planetary Physics, University of California, 405 Hilgard Ave., Los Angeles, CA 90095, United States

5RMA Aerospace Inc., Mountain View, CA, United States

6Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan

The unusually high solar wind pressure and strongly southward IMF on May 4, 1998 pushed the magnetopause well into the geosynchronous orbit, which exposed the POLAR satellite to the magnetosheath and solar wind. We use a gasdynamic convected field model to predict the magnetosheath quantities and then compare them with the in situ observations. The model prediction helps to reduce the uncertainty in the timing of the solar wind arrival time and provides a reference value for each physical parameter. It also helps to resolve the location of the satellite during strong magnetic fluctuations near the magnetopause. The plasma measurements from the TIDE instrument, in conjunction with the magnetometer measurements, indicate that there is a magnetospheric boundary layer during the event. There are also transient signatures near the magnetopause which may be caused by magnetospheric flux transfer events.