Frequency of Coronal Mass Ejection Impacts with Early Terrestrial Planets and Exoplanets around Active Solar-like Stars

Christina Kay,Vladimir S. Airapetian,Theresa Lüftinger,Oleg Kochukhov

doi:10.3847/2041-8213/ab551f

Abstract

Abstract Energetic flares and associated coronal mass ejections (CMEs) from young magnetically active solar-like stars can play a critical role in setting conditions for atmospheric escape as well as penetration of accelerated particles into their atmospheres that promotes formation of biologically relevant molecules. We have used the observationally reconstructed magnetic field of the 0.7 Gyr young Sun’s twin, k 1 Ceti, to study the effects of CME deflections in the magnetic corona of the young Sun and their effects on the impact frequency on the early Venus, Earth, and Mars. We find that the coronal magnetic field deflects the CMEs toward the astrospheric current sheet. This effect suggests that CMEs tend to propagate within a small cone about the ecliptic plane increasing the impact frequency of CMEs with planetary magnetospheres near this plane to ∼30% or by a factor of 6 as compared to previous estimate by Airapetian et al. Our model has important implications for the rise of prebiotic chemistry on early terrestrial planets as well as terrestrial-type exoplanets around young G-K dwarfs.

Highlights

The Hubble Space Telescope (HST), Kepler Space Telescope, and recent Transiting Exoplanet Survey Satellite (TESS) observations suggest that young and active F-M–type planet hosts are magnetically active stars showing evidence of strong surface magnetic fields, large starspots, and intense X-ray coronal emission
Our Forecasting a CME’s Altered Trajectory (ForeCAT) model results suggest that the global magnetic background of the star is important in the determining the deflection and rotation of stellar coronal mass ejections (CMEs), and a critical factor in determination of CME collision frequency with planetary magnetospheres
We used the observationally constrained magnetic environment of k1 Ceti, the young Sun’s twin, at two epochs separated by 11 months and applied our 3D model, ForeCAT to study the trajectories of CMEs and derive the representative frequencies of CME collision with early Venus, Earth, and Mars as well as exoplanets around young solar-like stars

Summary

Introduction

The Hubble Space Telescope (HST), Kepler Space Telescope, and recent Transiting Exoplanet Survey Satellite (TESS) observations suggest that young and active F-M–type planet hosts are magnetically active stars showing evidence of strong surface magnetic fields, large starspots, and intense X-ray coronal emission. For terrestrial-type exoplanets orbiting the young Sun and active stars, the dynamic and magnetic pressure from powerful (Carrington-type) CMEs can push the day-side planetary magnetosphere to a stand-off distance of the less than 2 planetary radii (Khodachenko et al 2007; See et al 2014; Airapetian et al 2016; Kay et al 2016; Garraffo et al 2017; Patsourakos & Georgoulis 2017) This widens the polar cap by opening 70% of the magnetospheric field and facilitating entry for energetic particles accelerated by CME-driven shocks.

Model Setup

ForeCAT Simulations

The Probabilistic CME Impact Model

Findings

Conclusion