Six Magnetic Field Models Compared:
Mapping Geosynchronous Orbit
to the Auroral Zone

Geoffrey D. Reeves
Loretta A. Weiss, Michelle F. Thomsen and David J. McComas
Los Alamos National Laboratory, Los Alamos NM

The Tsyganenko 1989 model accepts 6 values of Kp. The first 5 values are 0 to 4. The last value covers all Kp conditions Kp>4+.
Higher values of Kp move the foot points equatorward compared to low values of Kp for all local times. The Tsyganenko 1989 model does not show the effects of magnetopause compression during active conditions on the foot points of geosynchronous orbit.
The foot points predicted by the Tsyganenko 1989 model are always equatorward of the foot point predicted by the internal IGRF model alone.
For quiet conditions the Tsyganenko 1989 model has foot points which are substantially equatorward of the IGRF model foot points indicating that the field model is "stretched" even under Kp=0 conditions. (This is similar to the dependence of the Hilmer-Voigt model on equatorward edge in the midnight local time region.)
We suspect that, in order to get sufficient stretching at midnight for high Kp conditions the field is over-stretched at other local times and for low Kp conditions. (Note that relatively few dayside observations are included to constrain the model.)

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Last updated: Tuesday June, 20 1995