On the Comprehensive 3D Modeling of the Radiation Environment of Proxima Centauri b: A New Constraint on Habitability?

Abstract

The combined influence of stellar energetic particles and galactic cosmic rays (GCRs) on the radiation environment, and hence potential habitability, of Earth-like exoplanets is relatively unknown. The present study, for the first time, comprehensively models the transport of these particles in a physics-first manner, using a unique suite of numerical models applied to the astrosphere of Proxima Centauri. The astrospheric plasma environment is modeled magnetohydrodynamically, while particle transport is modeled using a 3D ab initio GCR modulation code, as opposed to previous 1D approaches to this problem. StEP intensities are also calculated using observed stellar event profiles for Proxima Centauri as inputs. Computed intensities are then used to calculate possible atmospheric ionization effects and dose rates. We demonstrate that the contribution of GCRs to these quantities is indeed significant, contrary to the conclusions of previous studies. Furthermore, we propose a novel potential constraint on exoplanetary habitability, namely the rotational period of the host star, based on the unique 3D modeling approach presented here.

Keywords

• Astrospheres
• Exoplanet atmospheres
• Galactic cosmic rays
• Solar energetic particles