M dwarfs can have Earth-like fluxes of Galactic cosmic rays in their habitable zones

The propagation of Galactic cosmic rays is well studied in the context of the Sun but it is poorly known in the context of M dwarfs. Quantifying the flux of cosmic rays reaching exoplanets is essential since they are important in the context of life. Here, we investigate the modulation of Galactic cosmic rays as they travel through the astrosphere of six M dwarfs. We perform simulations using a combined 1D cosmic ray transport model and 1D MHD stellar wind model. We found that, three M dwarfs in our sample have Galactic cosmic rays fluxes comparable with Earth’s around their much closer-in habitable zones. Most of the known exoplanets in our sample have a significantly lower flux of Galactic cosmic rays than values observed at the Earth. This includes GJ 273b which is the only known planet orbiting the habitable zone of its host star.