The Geomagnetic Field: 1970-1990 and the NASA Candidate Models for DGRF1985 and IGRF1990.

Abstract

All available magnetic data from observatories, satellites, repeat station measurements, and aeromagnetic, shipborne and land surveys are used to derive spherical harmonic models of the geomagnetic field from 1970 to 1990. Two models are derived, one using data from the DE-2 satellite the other not, since the quality of that data is unknown. These models are designated GSFC(11/90)D and GSFC(11/90) respectively. Main field coefficients are determined up to degree 13 and temporal variation, represented by B-splines, up to degree 10. Bias values at the fixed observatories were included as part of the solution. The secular variation models are smoothed by use of norm minimization. Both models fit the data very well.