Radiation-Hydrodynamics of Hot Jupiter Atmospheres

TL;DR

This paper explores the importance of radiation-hydrodynamics in modeling hot Jupiter atmospheres, highlighting how fast winds and relativistic effects can significantly influence radiative transfer and atmospheric observations.

Contribution

It introduces the concept that dynamic, wind-influenced radiative transfer in hot Jupiters requires coupled radiation-hydrodynamics modeling, a departure from traditional static approaches.

Findings

Doppler shifts distort line profiles in fast winds.

Flow-dependent deviations affect atmospheric emission and absorption.

Implications for accurate atmospheric modeling and interpretation.

Abstract

Radiative transfer in planetary atmospheres is usually treated in the static limit, i.e., neglecting atmospheric motions. We argue that hot Jupiter atmospheres, with possibly fast (sonic) wind speeds, may require a more strongly coupled treatment, formally in the regime of radiation-hydrodynamics. To lowest order in v/c, relativistic Doppler shifts distort line profiles along optical paths with finite wind velocity gradients. This leads to flow-dependent deviations in the effective emission and absorption properties of the atmospheric medium. Evaluating the overall impact of these distortions on the radiative structure of a dynamic atmosphere is non-trivial. We present transmissivity and systematic equivalent width excess calculations which suggest possibly important consequences for radiation transport in hot Jupiter atmospheres. If winds are fast and bulk Doppler shifts are indeed important for the global radiative balance, accurate modeling and reliable data interpretation for hot Jupiter atmospheres may prove challenging: it would involve anisotropic and dynamic radiative transfer in a coupled radiation-hydrodynamical flow. On the bright side, it would also imply that the emergent properties of hot Jupiter atmospheres are more direct tracers of their atmospheric flows than is the case for Solar System planets. Radiation-hydrodynamics may also influence radiative transfer in other classes of hot exoplanetary atmospheres with fast winds.