Circulation in the liquid core and coupling with the mantle

Abstract

Changes in the motions inside the Earth's molten core are associated with changes in the core's angular momentum and, as a consequence, in the mantle's angular momentum. These motions can be estimated because they are responsible for both the maintenance of the geomagnetic field through dynamo action and the high frequency variations of the field. It can be shown that they do not play an important part in the excitation of the Chandler wobble. On the other hand changes in the angular momentum carried by cylindrical annuli rigidly rotating about the rotation axis balance changes in the mantle's angular momentum inferred from length of the day observations. In this paper, torques acting between the core and the mantle are discussed. It proves helpful to consider these mechanisms on a broad range of timescales from 1 day (damping of the free core nutation) to 10 5 years (equilibration of the Earth's dynamo).