The Model of the Geomagnetic Non-Dipole Field

Abstract

Yukutake's model separates the geomagnetic field into drifting and standing parts, not only fits well to the observed field for the past several hundred years, but also emphasizig the regularities of the westward drift of the geomagnetic non-dipole field. However, there are still some problems to be reinvestigated:
a) In Yukutake's model the geomagnetic secular variation consists of only drifting parts, which is not consistent with the observed results;
b) The drift velocity depends on the order m of spherical functions. It is very difficult to understand its physical significance, or to imagine the configuration of its source field.
In this paper we make some modifications to Yukutake's model, having the standing part dependent on time, and adopting a uniform drift velocity ν=0.295°/yr.
The modified model is much more fitting to the observed fields than that of Yukutake's. The root-mean-square value of the differences between the main fields of the computed and the observed decreases by 50%, and that between the secular variations decreases even by 10%.
The more important fact is that the modified model can successfully minimize the above mentioned uncertainties of Yukutake's model.