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

It is essential to use the full IGRF field. Using a dipole for the internal field can cause a larger error in mapping than any differences in external field models.
It is sufficient to use 6 harmonics. Higher harmonics make negligible contributions to the location of the foot points of geosynchronous orbit.
The effect of higher harmonics varies with location. There is little difference over western Canada and large differences over Iceland and central Russia.
All field models in this study use the IGRF field for the internal field.
The IGRF field rotates with the earth and does not depend on local time.
The external fields which are superimposed on the IGRF field mainly depend on local time.
Therefore foot points depend on both local time and longitude.

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Last updated: Tuesday June, 20 1995