Atmospheric and oceanic excitation of the rotation of a three-layer Earth

¹ Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium e-mail: v.dehant@oma.be
² Institut de Physique du Globe, Paris, France

Received: 19 October 2004
Accepted: 24 February 2005

Abstract

In this paper, we evaluate the nutational Earth response to the excitation exerted by a surface fluid (atmosphere, ocean, and hydrology) for a simple Earth model, constituted of three homogeneous layers: a solid deformable inner-core, a liquid outer core, and an elastic mantle. Our formula, valid in the quasi-diurnal frequency band, includes two resonances, at the Free Core Nutation (FCN) and the Free Inner-Core Nutation (FICN). Additionally, we have evaluated the amplitudes of those wobbles in response to a random noise excitation. We show that, compared with the FCN signal, the resonance at the FICN frequency induced by a surface fluid layer only induces a very small signal in the Earth rotation, and that, with an excitation comparable to the one available at the FCN, the FICN would generate a signal at the Earth surface at the sub-micrometer level.