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A Simple Theory on the Dynamical Effects of a Stratified Fluid Core Upon Nutational Motion of the Earth

Published online by Cambridge University Press:  14 August 2015

Tetsuo Sasao ,
Shuhei Okubo  and
Masanori Saito
Tetsuo Sasao
Affiliation:
International Latitude Observatory of Mizusawa, Mizusawa, Iwate, 023 Japan
Shuhei Okubo
Affiliation:
Geophysical Institute, University of Tokyo, Tokyo, 113 Japan
Masanori Saito
Affiliation:
Geophysical Institute, University of Tokyo, Tokyo, 113 Japan

Abstract

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The theory of Molodensky (1961) on dynamical effects of a stratified fluid outer core upon nutations and diurnal Earth tides is reconstructed on a new and probably much simpler ground. A theory equivalent to Molodensky's is well represented on the basis of two linear equations for angular-momentum balance of the whole Earth and the fluid outer core, which differ from the well-known equations of Poincaré (1910) only in the existence of products of inertia due to deformations of the whole Earth and fluid outer core. The products of inertia are characterized by four parameters which are easily computed for every Earth model by the usual Earth tide equations. A reciprocity relation exists between two of the parameters. The Adams-Wiliamson condition is not a necessary premise of the theory. Amplitudes of nutations and tidal gravity factors are computed for three Earth models. A dissipative core-mantle coupling is introduced into the theory qualitatively. The resulting equations are expressed in the same form as those of Sasao, Okamoto and Sakai (1977). Formulae for secular changes in the Earth-Moon system due to the core-mantle friction are derived as evidences of internal consistency of the theory.

Type
Session IV
Information
Symposium - International Astronomical Union , Volume 78: Nutation and the Earth's Rotation , 1980 , pp. 165 - 183
Copyright
Copyright © Reidel 1980 

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