The Geomagnetic Field at 1982 from DE-2 and Other Magnetic Field Data

Abstract

Data from the DE-2 spacecraft for September 30, 1981 through January 6, 1983 are combined with data from the MAGSAT spacecraft, from magnetic observatories and from magnetic surveys to derive a geomagnetic field model for the period 1979.5 through 1983.5. Called GSFC(11/87), this model is virtually identical to the GSFC(12/83) model at 1980 and may be regarded as an extention of that model in time to 1983.5. Constant and first derivative (i.e., secular variation) internal coefficients are determined through degree and order 13; first degree external coefficients are determined as a function of the Dst index; and the solution includes calculation of fixed biases, or anomalies, for the observatory data. The MAGSAT and DE-2 data provide very good global data distribution at two epochs. The observatory and survey data distribution is not as good but does adequately link the two satellite epochs so that the resulting secular variation model is of high quality, at least to degree 9. Although DE-2 acquired vector data, preliminary modeling showed that its attitude accuracy was not adequate for satisfactory spherical harmonic analysis of the geomagnetic field. However, the scalar magnitude data are of good quality. Plots of the secular variation are given for three components and the field magnitude. The resulting model differs significantly from the IGRF, again demonstrating the need for satellite data in geomagnetic field modeling. © 1988, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.