Concerning thermal tides on hot Jupiters

TL;DR

This paper examines the impact of thermal tides on hot Jupiters and finds that, due to their atmospheric structure, thermal tides are unlikely to cause nonsynchronous rotation or noncircular orbits, contrary to previous suggestions.

Contribution

It demonstrates that the coupling of thermal and gravitational tides in hot Jupiters is negligible at zeroth order, challenging earlier claims about thermal tides inducing nonsynchronous rotation.

Findings

Thermal tides are suppressed in hot Jupiters due to their atmospheric structure.

The effect of thermal tides probably opposes the excitation of nonsynchronous rotation.

Coupling effects are negligible at zeroth order, with next order effects likely reinforcing synchronous states.

Abstract

By analogy with a mechanism proposed by Gold and Soter to explain the retrograde rotation of Venus, Arras and Socrates suggest that thermal tides may excite hot jovian exoplanets into nonsynchronous rotation, and perhaps also noncircular orbits. It is shown here that because of the absence of a solid surface above the convective core of a jovian planet, the coupling of the gravitational and thermal tides vanishes to zeroth order in the ratio of the atmospheric scale height to the planetary radius. At the next order, the effect probably has the sign opposite to that claimed by the latter authors, hence reinforcing synchronous and circular orbits.