KINEMATIC MAGNETIC-FIELD MORPHOLOGY AT THE CORE-MANTLE BOUNDARY

The earth's magnetic field is generated by induction in fluid motions in the liquid iron core, a dynamo process that is not yet properly understood. The field changes on time-scales of years to centuries, and this change probably forms part of the fundamental regeneration process. A kinematic approach is used whereby the induction of fluid motions is modelled by choosing a flow and investigating the magnetic field that it generates. Using a novel matching condition, which is appropriate when the upper part of the liquid iron core is static, a set of kinematic dynamos is generated that belongs to the geophysically interesting class of flows with one cell in radius. The morphology of the radial component of the induced magnetic field is then mapped at the boundary of the core and compared with equivalent maps derived from observation to retrieve some essential, symmetric static features in the geomagnetic held.