Abstract
We address in this paper the possible effects of motions in the fluid core on the Earth’s rotation, both length of day and pole motion. The geomagnetic field is thought to be generated by dynamo action in the conducting core; information on the fluid motion is then obtained through the study of the secular variation of this field.
A correlation between the time variations of some parameters of the geomagnetic field and the time variations of the rotation rate of the Earth which has been proposed some years ago (Le Mouël et al.,1981) is extended using recent data which do seem to buttress it. Magnetic variations lead rotation variations by some ten or fifteen years. Two mechanisms of core mantle coupling which would allow exchange of angular momentum between the core and the mantle and account for the observed correlation are briefly discussed.
The core motions can also have an effect on the pole motion: the pressure field associated with the time varying motions at the coremnantle boundary, which generate the secular variation, can act on the elastic mantle and change its inertia products. The excitation function corresponding to this mechanism is shown to have such an order of magnitude that it could contribute to maintain the Chandler wobble again dissipation. Its efficiency depends on the time constant of the secular variation.
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Gire, C., Le Mouël, J.L. (1986). Flow in the fluid core and Earth’s rotation. In: Cazenave, A. (eds) Earth Rotation: Solved and Unsolved Problems. NATO ASI Series, vol 187. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-4750-4_17
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DOI: https://doi.org/10.1007/978-94-009-4750-4_17
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