Semidiurnal thermal tides in asynchronously rotating hot Jupiters

TL;DR

This paper models the thermal tide response of hot Jupiters, revealing how resonances and rotation can induce asynchronous atmospheric rotation through tidal torques.

Contribution

It develops a comprehensive global model for thermal tides in rotating, non-adiabatic hot Jupiters, extending previous approaches and analyzing tidal torque and resonance effects.

Findings

Resonances amplify tidal torque significantly in 1-30 day periods.

Rotation couples forcing to Hough modes, affecting tidal response.

Radiative cooling moderates the amplitude of tidal resonances.

Abstract

Thermal tides can torque the atmosphere of hot Jupiters into asynchronous rotation, while these planets are usually assumed to be locked into spin-orbit synchronization with their host star. In this work, our goal is to characterize the tidal response of a rotating hot Jupiter to the tidal semidiurnal thermal forcing of its host star, by identifying the structure of tidal waves responsible for variation of mass distribution, their dependence on the tidal frequency and their ability to generate strong zonal flows. We develop an ab initio global modeling that generalizes the early approach of Arras & Socrates (2010) to rotating and non-adiabatic planets. We derive analytically the torque exerted on the body and the associated timescales of evolution, as well as the equilibrium tidal response of the atmosphere in the zero-frequency limit. Finally, we integrate numerically the equations of thermal tides for three cases including dissipation and rotation step by step. The resonances associated with tidally generated gravito-inertial waves amplify significantly the resulting tidal torque in the range 1-30 days. This torque can drive globally the atmosphere into asynchronous rotation, as its sign depends on the tidal frequency. The resonant behaviour of the tidal response is enhanced by rotation, which couples the forcing to several Hough modes in the general case, while the radiative cooling tends to regularize it and diminish its amplitude.