SPHERICAL CAP HARMONIC-ANALYSIS OF THE GEOMAGNETIC-FIELD OVER EAST-ASIA

Based on the geomagnetic data from repeat stations and observatories, the spherical cap harmonic model of the geomagnetic field over East As ia was derived. The pole of the spherical cap is at 45 degrees N and 1 05 degrees E and the half-angle of the spherical cap is 45 degrees. Th e maximum index of the spherical cap harmonic analysis is 12, giving t he minimum wavelength of 1635 km. The root mean square deviation value s of the spherical cap harmonic model are 122.8 (north component), 103 .4 (east component) and 128.0 nT (vertical component). The geomagnetic charts of East Asia were drawn at epoch 1980.0 from the spherical cap harmonic model. Furthermore, the deviation of the spherical cap harmo nic model from DGRF 1980 was calculated, and the corresponding contour charts were drawn.