What causes such major changes is not known. Several years ago, Gary A. Glatzmier of Los Alamos National Laboratory and Paul H. Roberts of the University of California, Los Angeles achieved a remarkable breakthrough in the mathematical modeling of the geomagnetic field. They solved the equations of electromagnetism and magnetohydrodynamics for the outer core and thereby obtained a computer simulation of the geomagnetic field. The simulation yielded relatively long periods, when the field was roughly aligned with the rotation axis, that were separated by a rapid flipping of the poles. During this simulated reversal, the non-dipole field became dominant.
Attempts are now underway to determine the morphology of the transitional fields during reversals.
And it is hoped that these results will inspire still more realistic models and a better understanding of the working of the geodynamo. We programmed supercomputers to solve the large set of nonlinear equations that describe the physics of the fluid motions and magnetic field generation in the Earth's core. Magnetic field lines are blue where the field is directed inward and yellow where it is directed outward. The simulated geomagnetic field, which now spans the equivalent of over 300,000 years, has an intensity, a dipole-dominated structure and a westward drift at the surface that are all similar to the Earth's real field. Our model predicted that the solid inner core, being magnetically coupled to the eastward fluid flow above it, should rotate slightly faster than the surface of the Earth.