The anelastic equilibrium tide in exoplanetary systems

TL;DR

This paper models the equilibrium tide in solid planetary cores with anelastic properties, analyzing how internal structure and rheology influence tidal dissipation, with implications for understanding exoplanet interior properties.

Contribution

It provides a detailed theoretical framework for calculating Love numbers and tidal quality factors in solid planetary regions considering anelasticity and fluid envelopes.

Findings

Tidal dissipation depends on core size and rheology.

Solid core dissipation can compete with fluid layer dissipation.

Frequency-dependent dissipation mechanisms vary among planet types.

Abstract

Earth-like planets have anelastic mantles, whereas giant planets may have anelastic cores. As for the fluid parts of a body, the tidal dissipation of such solid regions, gravitationally perturbed by a companion body, highly depends on its internal friction, and thus on its internal structure. Therefore, modelling this kind of interaction presents a high interest to provide constraints on planet interiors, whose properties are still quite uncertain. Here, we examine the equilibrium tide in the solid central region of a planet, taking into account the presence of a fluid envelope. We first present the equations governing the problem, and show how to obtain the different Love numbers that describe its deformation. We discuss how the quality factor Q depends on the rheological parameters, and the size of the core. Taking plausible values for the anelastic parameters, and examinig the frequency-dependence of the solid dissipation, we show how this mechanism may compete with the dissipation in fluid layers, when applied to Jupiter- and Saturn-like planets. We also discuss the case of the icy giants Uranus and Neptune.