MAGNETIC-FIELD REVERSAL RESULTING FROM A DYNAMO PROCESS IN A SPHERICAL-SHELL

The magnetic field is one of the intrinsic properties of the Earth, originating in a magnetohydrodynamic (MHD) process in the liquid outer core. It also exhibits a variety of features of secular variation; most typically, reversals of the polarity of the axial dipole term and westward drifts of the non-zonal terms. Here we report on the results of our simulations of an MHD dynamo process in a rotating spherical shell and demonstrate that the above two typical features of the Earth's magnetic field can be understood quite naturally without any specific conditions. We also examine how the virtual geomagnetic pole (VGP) moves, in our MHD dynamo model, during transitional stages from one polarity to the other, and show that some features of the transitional behaviour derived from the paleomagnetic data can be seen in our dynamo model as well.