Core Dynamics and the Geodynamo

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Roberts EAR-0074015 The magnetic field of the Earth is created by electric currents flowing in the Earth's molten-iron core. These currents are generated by self-excited dynamo action. As in a power station, the motion of the conductor in the presence of the magnetic field produces the currents that create the magnetic field itself. The energy source for the fluid motions in the Earth's core is commonly supposed to be the thermal and compositional buoyancy of material released at the surface of the solid inner core as the Earth cools, and successful geodynamo simulations have been based on this idea. There is also a second possible energy source, the luni-solar precession of the Earth's axis of rotation. This has never been evaluated as a possible source of the Earth's magnetism. It is the object of this investigation to determine whether precession can maintain a geodynamo that creates an Earth-like field. If it fails to do so, the aim will be to find how precessional forces alter the fields produced by the successful buoyancy-driven geodynamo.