The dynamics of the Earth's inner and outer cores

Abstract

A brief historical introduction to the study of the Earth's core is followed by a review of recent advances in the dynamics of the liquid outer core and the rotation of the solid inner body. In particular, the scaling of the fluid motion equations is reviewed and a detailed derivation of the 'subseismic equation' which governs small-amplitude, low-frequency oscillations is given following methods first outlined by Rochester. Attention is given to the compressibility of the outer core and its role in dynamo theory as well as its effect on Proudman-Taylor flow, where it produces a fluid motion with helicity. The theorem of J.B. Taylor is also generalised to real core compressibility. Rotational motions of the inner core are examined under the strong gravity torque exerted on it by the rest of the Earth. Both the motion ignoring back reaction on the mantle's rotation and the full coupled problem are solved.