# Atmospheric effects of stellar cosmic rays on Earth-like exoplanets orbiting M-dwarfs

Abstract : M-dwarf stars are generally considered favourable for rocky planet detection. However, such planets may be subject to extreme conditions due to possible high stellar activity. The goal of this work is to determine the potential effect of stellar cosmic rays on key atmospheric species of Earth-like planets orbiting in the habitable zone of M-dwarf stars and show corresponding changes in the planetary spectra. We build upon the cosmic rays model scheme of Grenfell et al. (2012), who considered cosmic ray induced NOx production, by adding further cosmic ray induced production mechanisms (e.g. for HOx) and introducing primary protons of a wider energy range (16 MeV - 0.5 TeV). Previous studies suggested that planets in the habitable zone that are subject to strong flaring conditions have high atmospheric methane concentrations, while their ozone biosignature is completely destroyed. Our current study shows, however, that adding cosmic ray induced HOx production can cause a decrease in atmospheric methane abundance of up to 80\%. Furthermore, the cosmic ray induced HOx molecules react with NOx to produce HNO$_3$, which produces strong HNO$_3$ signals in the theoretical spectra and reduces NOx-induced catalytic destruction of ozone so that more than 25\% of the ozone column remains. Hence, an ozone signal remains visible in the theoretical spectrum (albeit with a weaker intensity) when incorporating the new cosmic ray induced NOx and HOx schemes, even for a constantly flaring M-star case. We also find that HNO$_3$ levels may be high enough to be potentially detectable. Since ozone concentrations, which act as the key shield against harmful UV radiation, are affected by cosmic rays via NOx-induced catalytic destruction of ozone, the impact of stellar cosmic rays on surface UV fluxes is also studied.
Keywords :
Type de document :
Article dans une revue
Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 585, pp.A96. 〈10.1051/0004-6361/201425602〉

Littérature citée [59 références]

https://hal-insu.archives-ouvertes.fr/insu-01351244
Contributeur : Nathalie Pothier <>
Soumis le : mercredi 21 septembre 2016 - 16:24:21
Dernière modification le : jeudi 7 février 2019 - 16:06:02
Document(s) archivé(s) le : jeudi 22 décembre 2016 - 13:13:53

### Fichier

1511.04920v1 (1).pdf
Fichiers éditeurs autorisés sur une archive ouverte

### Citation

F. Tabataba-Vakili, J. L. Grenfell, Jean-Mathias Grießmeier, H. Rauer. Atmospheric effects of stellar cosmic rays on Earth-like exoplanets orbiting M-dwarfs. Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 585, pp.A96. 〈10.1051/0004-6361/201425602〉. 〈insu-01351244〉

### Métriques

Consultations de la notice

## 245

Téléchargements de fichiers