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W. B. Moore (UCLA)
Tidal dissipation occurs within satellites such as Io or Europa as a consequence of viscoelastic deformation within the satellite. This deformation occurs on very large length scales, as does the corresponding dissipation (spherical harmonic degree 2-4). The material properties of the body (viscosity, shear modulus), however, may change on much smaller length scales, due to convective plumes, for example. The degree of coupling between the lateral variations in viscosity and dissipation depend on the relative length scales; efficient coupling requires similar scales. Analytical and numerical results will be presented to demonstrate this. The conclusion is that tidal dissipation, while closely coupled to the degree 2-4 variations in material properties, is completely uncoupled to the convectively produced variations, unless the convecting zone is somehow at very low Rayleigh number and occupies most of the satellite's interior. As far as convection is concerned, tidal dissipation is a very slowly varying internal heating term, uncoupled to the lateral viscosity variations produced by convection.