Atmospheres of Hot Super-Earths

TL;DR

This study models the minimal atmospheres of hot super-Earths, revealing their limited extent, the influence of magnetic effects, and potential observable signatures in reflection and emission spectra.

Contribution

It provides the first hydrodynamic analysis of hot super-Earth atmospheres including magnetic effects and predicts their observational signatures.

Findings

Atmospheric pressures stay near saturation values.

Strong winds do not extend atmospheres beyond day-night terminators.

Magnetic effects can significantly alter atmospheric behavior.

Abstract

Hot super-Earths likely possess minimal atmospheres established through vapor saturation equilibrium with the ground. We solve the hydrodynamics of these tenuous atmospheres at the surface of Corot-7b, Kepler 10b and 55 Cnc-e, including idealized treatments of magnetic drag and ohmic dissipation. We find that atmospheric pressures remain close to their local saturation values in all cases. Despite the emergence of strongly supersonic winds which carry sublimating mass away from the substellar point, the atmospheres do not extend much beyond the day-night terminators. Ground temperatures, which determine the planetary thermal (infrared) signature, are largely unaffected by exchanges with the atmosphere and thus follow the effective irradiation pattern. Atmospheric temperatures, however, which control cloud condensation and thus albedo properties, can deviate substantially from the irradiation pattern. Magnetic drag and ohmic dissipation can also strongly impact the atmospheric behavior, depending on atmospheric composition and the planetary magnetic field strength. We conclude that hot super-Earths could exhibit interesting signatures in reflection (and possibly in emission) which would trace a combination of their ground, atmospheric and magnetic properties.