Habitability of terrestrial planets around active M-stars. The effect of stellar radiation and cosmic rays upon climate and photochemistry

Planetary habitability depends strongly on the interaction between the planetary atmosphere and the energy from its host star. Due to both the anticipated diversity of exoplanetary atmospheres as well as the large range of stellar classes and activities, modeling possible planetary climate states and atmospheric conditions is a challenging endeavor. A central aim of this work was to extend the understanding of the effects of stellar radiation upon atmospheric temperatures, and the multitude of cascading effects which Stellar Energetic Particles together with Galactic Cosmic Rays may have upon atmospheric composition. Both these effects are likely to be key factors affecting potential surface habitability. This thesis therefore addressed the following scientific questions for some well-chosen scenarios: - What kind of atmospheres may provide habitable conditions? - Which atmospheres can explain observed spectral features? - How does the host star ́s spectral type affect planetary habitability? - How do energetic particle showers impact atmospheric composition and habitability? To address these questions, a comprehensive one-dimensional coupled climate chemistry model was developed and applied during the course of this cumulative thesis. Part of this thesis are the works published in Scheucher et al. (2018) and Scheucher et al. (2020a) focusing on the effect of energetic particle bombardment onto exoplanetary atmospheres and habitability, and Scheucher et al. (2020b) focusing on the effect of opacities in radiative transfer through a large variety of atmospheric conditions upon planetary climate and atmospheric spectral characteristics.