Spherical Harmonic Analyses of the Geomagnetic Field for Eight Epochs between 1600 and 1910

Abstract

The data for epochs between 1600 and 1910 in the catalogue of Veinberg and Shibaev have been analysed and two sets of spherical harmonic models of the geomagnetic field have been derived. Two methods are used to overcome the shortage of intensity data for the earlier epochs. In the first set of models the ratios of the harmonic coefficients to g10 are determined using both D and I data. The second set uses assumed values of g10 for these epochs. In contrast to previous analyses based on this catalogue, the data are weighted according to the number of original observations contributing to the catalogue mean and allowance is made for the oblateness of the Earth. The dipolar nature of the field in the Pacific region is investigated and the positions of the geomagnetic poles are derived. The variation of the position of the eccentric dipole with time is studied. Copyright © 1974, Wiley Blackwell. All rights reserved