Thermal tides on rocky planets through a novel fully analytical solution

TL;DR

This paper introduces a new fully analytical model for thermal tides on rocky planets, enabling better understanding of their atmospheric dynamics and long-term rotational evolution, with applications to exoplanets and Earth's history.

Contribution

A novel closed-form analytical solution for planetary thermal tides derived from first principles, applicable to dry or moist atmospheres, and validated against complex models.

Findings

Accurately predicts Earth's semidiurnal thermotidal response.

Captures key features of thermotidal torque from GCMs.

Provides insights into Earth's day length evolution during Precambrian.

Abstract

Thermal tides are atmospheric tides caused by variations in day-night insolation, similar to gravitational tides but with key differences. While both result in delayed mass redistribution, energy dissipation, and angular momentum exchanges between the planet and its host star, thermal tides can drive a planet's dynamics away from the rotational equilibrium states predicted by classical tidal theory. In this work, we present a novel closed-form solution for the thermotidal response of rocky planets. This general solution is derived from first principles, assuming either dry or moist adiabatic temperature profiles for the planet's atmosphere, and can be readily applied to study the long-term evolution of exoplanets in the habitable zones of their host stars. Despite relying on a small number of parameters, the model successfully captures the key features of the thermotidal torque predicted by General Circulation Models (GCMs). It also accurately predicts Earth's current semidiurnal thermotidal response and provides new insights into the evolution of the length of day during the Precambrian era.