Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences

TL;DR

This paper presents a 3D model combining analytic theory and numerical simulations to explain how heat redistribution in hot Jupiter atmospheres depends on factors like temperature, radiative cooling, and magnetic effects, revealing wave-mediated temperature differences.

Contribution

The study introduces a comprehensive 3D model that links wave dynamics, radiative processes, and magnetic drag to the observed temperature differences in hot Jupiter atmospheres.

Findings

Radiative cooling and heating dominate wave damping at higher temperatures.

Frictional drag from magnetic effects increases with temperature and influences heat redistribution.

Dayside-nightside temperature differences grow with stellar irradiation and decrease with atmospheric pressure.

Abstract

The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing dayside-to-nightside brightness temperature difference with increasing equilibrium temperature. Here we present a three-dimensional model that explains this relationship, in order to shed insight on the processes that control heat redistribution in tidally-locked planetary atmospheres. This three-dimensional model combines predictive analytic theory for the atmospheric circulation and dayside-nightside temperature differences over a range of equilibrium temperature, atmospheric composition, and potential frictional drag strengths with numerical solutions of the circulation that verify this analytic theory. This analytic theory shows that the longitudinal propagation of waves mediates dayside-nightside temperature differences in hot Jupiter atmospheres, analogous to the wave adjustment mechanism that regulates the thermal structure in Earth's tropics. These waves can be damped in hot Jupiter atmospheres by either radiative cooling or potential frictional drag. This frictional drag would likely be caused by Lorentz forces in a partially ionized atmosphere threaded by a background magnetic field, and would increase in strength with increasing temperature. Additionally, the amplitude of radiative heating and cooling increases with increasing temperature, and hence both radiative heating/cooling and frictional drag damp waves more efficiently with increasing equilibrium temperature. Radiative heating and cooling play the largest role in controlling dayside-nightside temperature temperature differences in both our analytic theory and numerical simulations, with frictional drag only important if it is stronger than the Coriolis force. As a result, dayside-nightside temperature differences in hot Jupiter atmospheres increase with increasing stellar irradiation and decrease with increasing pressure.