Precession and the Earth's Magnetic Field

Abstract

IT is generally agreed that the Earth's principal magnetic field arises from a dynamo action in the fluid and electrically conducting core, although the origin of motions in the core is still a matter for speculation. Only two mechanisms seem to be possible-thermal convection in the core or precession of the Earth¹. Experiments by Malkus² have indicated that the core would not precess with the mantle like a rigid body as had previously been thought. A detailed theory of a dynamo in a processing turbulent core is difficult and only order of magnitude calculations have so far been attempted. Such order of magnitude arguments depend quite critically on the value of the electrical conductivity, σ, of the core.