Global flow regimes of hot Jupiters

TL;DR

This study investigates how stellar irradiation and atmospheric composition influence the global circulation patterns of hot Jupiters, revealing a transition from jet-dominated to day-to-night flows with increasing temperature.

Contribution

It introduces a wavelet-based analysis method and provides new insights into how irradiation and molecular weight affect atmospheric flow regimes in hot Jupiters.

Findings

Increased stellar irradiation reduces heat redistribution efficiency.

Higher temperatures lead to dominance of large-scale wave modes.

Lowering molecular weight partially restores circulation complexity.

Abstract

In hot and ultra-hot Jupiters, stellar irradiation is a primary driver of atmospheric circulation and the wave structures that sustain it. We aim to investigate how variations in radiative and dynamical timescales influence global flow regimes, atmospheric circulation efficiency, and the interplay of wave structures across a sample of hot Jupiters. In particular, we explore a previously predicted transition in the global flow regime, where enhanced stellar irradiation suppresses the smaller-scale wave and eddy features that feed into superrotating jets and ultimately leads to simpler, day-to-night dominated flows. We simulate a suite of eight well-studied hot Jupiters with the THOR general circulation model, spanning equilibrium temperatures from about $1100$ K to $2400$ K. We develop a wavelet-based analysis method to decompose simulated wind fields into their underlying wave modes, which we validate on analytical examples. As a preliminary exploration of the flow regime of ultra-hot Jupiters, we perform an additional simulation for WASP-121b, where the mean molecular weight is set to represent an atmosphere dominated by atomic hydrogen. Our results confirm that increasing stellar irradiation diminishes atmospheric heat redistribution efficiency and weakens contributions from smaller-scale modes that are critical to sustain superrotation. As equilibrium temperatures rise, large-scale modes dominate the atmospheric circulation, driving a transition from jet-dominated flows toward day-to-night circulation. Additionally, by artificially lowering the mean molecular weight, we partially restore circulation efficiency and reintroduce a more complex, multi-scale flow pattern. These findings refine our understanding of how atmospheric circulation evolves with increasing irradiation and composition changes, offering a more nuanced framework for interpreting hot and ultra-hot Jupiter atmospheres.