Abstract The impact of stellar energetic particles (StEPs) and galactic cosmic rays (GCRs) on exoplanetary atmospheres, and with that on transmission spectra and biosignatures like methane and ozone, recently became one of the foci of exoplanetary habitability studies. Deriving the exoplanetary radiation field, however, is an interdisciplinary task starting with astrospheric modeling. Although multi-wavelength observations of the Hubble Space Telescope, Kepler, and TESS helped to study the characteristics of planet-hosting cool stars. However, features like stellar wind speeds and mass-loss rates mandatory for astrospheric modeling can only be indirectly derived. Here, a brief review of the astrospheric modeling efforts of three M stars and the transport of cosmic rays within is presented. Using a unique suite of numerical models, the astrospheric plasma environment is modeled magnetohydrodynamically (3D), and the particle transport is modeled using an ab initio GCR modulation code. A recent model effort deriving flare-induced StEP intensities is also discussed.
Herbst et al. (Sun,) studied this question.