Flows, Circulations, and Energy Transport in the Outer and Deep Atmospheres of Synchronous and Non-synchronous Hot Jupiters

TL;DR

This study investigates how rotation and (non)synchronicity influence atmospheric flows and energy transport in hot Jupiters, revealing distinct dynamical regimes and a persistent night-side hot-spot at slow rotation rates.

Contribution

It provides a comprehensive analysis of the impact of rotation rates on atmospheric dynamics of hot Jupiters using long-timescale models, highlighting new regimes and features.

Findings

Different rotation regimes affect vertical transport and hot-spot formation.

Non-synchronicity influences the stability of atmospheric structures.

A persistent night-side hot-spot appears at slow rotation rates.

Abstract

Recent studies have shown that vertical enthalpy transport can explain the inflated radii of highly irradiated gaseous exoplanets. They have also shown that rotation can influence this transport, leading to highly irradiated, rapidly rotating, objects that are uninflated. Here we explore the underlying flows, including the impact of (non)synchronous rotation. We use DYNAMICO to run a series of long-timescale, HD209-like, atmospheric models at various surface rotation rates. For models that are tidally-locked, we consider rotation rates between $1/16^\mathrm{th}$ and $40$ times the rotation rate of HD209, whilst for non-synchronous models we consider the range $1/8^\mathrm{th}$ to $4$x. We find that our synchronous models fall into one of three $\Omega$-dependent regimes: at low $\Omega$, we find that the outer atmosphere dynamics are driven by a divergent day-night wind, driving weak vertical transport and the formation of a night-side hot-spot. At intermediate $\Omega$, we find classical hot Jupiter dynamics, whilst at high $\Omega$ we find a strong Coriolis effect that suppresses off-equator dynamics, including the jet-driving standing waves, thus also reducing vertical transport. As for non-synchronicity, when small, we find that it has little effect on dynamics. However as it grows, we find that temporal variations prevents the formation of the persistent structures that drive global dynamics. We find that rotation can significantly impact the atmospheric dynamics of irradiated exoplanets, including vertical advection, which may explain the scatter in the radius-irradiation relation. We have also identified a seemingly robust feature at slow rotation: a night-side hot-spot. As this may have important implications for both the phase curve and atmospheric chemistry, we suggest that this study be followed up with next-generation GCMs that robustly model radiation/chemistry.