Gravity Waves on Hot Extrasolar Planets: I. Propagation and Interaction with the Background

TL;DR

This paper investigates how gravity waves influence the atmospheres of hot extrasolar planets, showing they can significantly alter flow speeds, heat distribution, and momentum transfer, which are crucial for accurate atmospheric modeling.

Contribution

It provides a detailed analysis of gravity wave dynamics on hot exoplanets and discusses their impact on atmospheric flow, heating, and heat redistribution, advancing understanding of planetary atmospheres.

Findings

Gravity waves can significantly accelerate or decelerate atmospheric flow.

Gravity waves can provide substantial heating (~100-1000 K per rotation).

Waves facilitate heat and momentum transfer from dayside to nightside.

Abstract

We study the effects of gravity waves, or g-modes, on hot extrasolar planets. These planets are expected to possess stably-stratified atmospheres, which support gravity waves. In this paper, we review the derivation of the equation that governs the linear dynamics of gravity waves and describe its application to a hot extrasolar planet, using HD209458 b as a generic example. We find that gravity waves can exhibit a wide range of behaviors, even for a single atmospheric profile. The waves can significantly accelerate or decelerate the background mean flow, depending on the difference between the wave phase and mean flow speeds. In addition, the waves can provide significant heating (~100 to ~1000 K per planetary rotation), especially to the region of the atmosphere above about 10 scale heights from the excitation region. Furthermore, by propagating horizontally, gravity waves provide a mechanism for transporting momentum and heat from the dayside of a tidally locked planet to its nightside. We discuss work that needs to be undertaken to incorporate these effects in current atmosphere models of extrasolar planets.