The Secular Variation Characteristics and Mechanisms of Geomagnetic Field

The variations of geomagnetic field are divided into three parts: the spontaneous variations of dipole and non-dipole geomagnetic fields and the dipole geomagnetic field variation resulting from geomagnetic anomalies of non-dipole field through modulating the ring current in core-mantle boundary. The secular variation characteristics and distributions of geomagnetic field at different depths are calculated and analyzed in this paper by using the model of International Geomagnetic Reference Field (1900~2000). Possible mechanisms are discussed also. It can be concluded that the westward driftage and reversal of geomagnetic field are not only resulted from non-dipole field, but also dipole.