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 1982 model [Tsyganenko-Usmanov, 1982] is quite different from the 1987 and 1989 versions.
Kp can take on 11 values, 0, 0+, 1-, 1, 1+, etc. up to 3+. The 11th value covers all conditions Kp>3+.
All dayside foot points in the Tsyganenko 1982 model are poleward of the IGRF foot points. This is consistent with compression of the field on the day side. However, the low Kp foot points are poleward of the high Kp foot points which is equivalent to less compression for higher Kp conditions. (Statistics show more compression is correlated with high Kp conditions.)
For the same value of Kp the foot points in the Tsyganenko 1982 model are further equatorward than the foot points in the Tsyganenko 1989 model indicating that the 1982 model is more stretched at midnight. This includes Kp=0 which is more stretched than in the other Tsyganenko models.
Unlike the Tsyganenko 1987 model, the dependence of the foot point on Kp is maximum at midnight (as expected).
The dependence of the foot point on Kp at midnight is similar in magnitude to that in the Tsyganenko 1989 model for Kp=0-4 but the Tsyganenko 1989 model goes to higher Kp values.
Because Kp can take on 11 values in the Tsyganenko 1982 model it is more continuously adjustable than the Tsyganenko 1987 or 1989 models.

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Last updated: Tuesday June, 20 1995