THE POLOIDAL GEOMAGNETIC FIELD IN A DIFFERENTIALLY ROTATING UPPER CORE LAYER

Abstract

This paper deals with the inverse solution of the induction equation accounting for moving core material. In a layer of the fluid outer core we prescribe the associated velocity field by a differential rotation. The angular velocity near the core–mantle boundary (CMB) corresponds to the mean westward drift of the geomagnetic field. We solve the induction equation for the poloidal magnetic field in both the mantle and the fluid outer-core layer using the magnetic field as the boundary value at the Earth's surface and the assumed velocity field as the prescribed model parameter. The numerical solution of the induction equation is based on a modified Tikhonov regularization of an integral equation approach described in a previous paper by Ballani et al..