Geomagnetic secular variation and motion of the earth's core

Summary A general theory of a time-dependent magnetic dipole in the earth is discussed. On the basis of the weastward drift of the «equatorial» dipole in the two eccentric dipoles model due toH. G. Macht, the impossibility of the origin of geomagnetic secular variation being in a deep interior of the earth's core is established from the standpoints of the shielding effect and the motions in the core. But the westward drift of the core's top layer relative to the mantle seems to be quite reasonable, even if we take into account the shielding effect of the mantle.