The Sun and stars as the primary energy input in planetary atmospheres

TL;DR

This paper reviews how the Sun and low-mass stars influence planetary atmospheres through their energy output and particle emissions, highlighting current understanding and gaps in modeling stellar fluxes and winds.

Contribution

It provides a comprehensive review of stellar flux and particle emissions and their effects on planetary atmospheres, emphasizing recent progress and remaining uncertainties.

Findings

Stellar flux impacts planetary atmosphere structure and evolution.

High-energy emissions are less understood than photospheric emissions.

Stellar wind evolution significantly affects planetary atmospheres.

Abstract

Proper characterization of the host star to a planet is a key element to the understanding of its overall properties. The star has a direct impact through the modification of the structure and evolution of the planet atmosphere by being the overwhelmingly larger source of energy. The star plays a central role in shaping the structure, evolution, and even determining the mere existence of planetary atmospheres. The vast majority of the stellar flux is well understood thanks to the impressive progress made in the modeling of stellar atmospheres. At short wavelengths (X-rays to UV), however, the information is scarcer since the stellar emission does not originate in the photosphere but in the chromospheric and coronal regions, which are much less understood. The same can be said about particle emissions, with a strong impact on planetary atmospheres, because a detailed description of the time-evolution of stellar wind is still lacking. Here we review our current understanding of the flux and particle emissions of the Sun and low-mass stars and briefly address their impact in the context of planetary atmospheres.