The strong suppression of Galactic cosmic rays reaching AU Mic b, c and Prox Cen b

Abstract

The propagation of Galactic cosmic rays is well understood in the context of the solar system but is poorly studied for M dwarf systems. Quantifying the flux of cosmic rays reaching exoplanets is important since cosmic rays are relevant in the context of life. Here, we calculate the Galactic cosmic ray fluxes in AU Mic and Prox Cen planetary systems. We propagate the Galactic cosmic rays using a 1D cosmic ray transport model. We find for Prox Cen b, AU Mic b and AU Mic c that the Galactic cosmic ray fluxes are strongly suppressed and are lower than the fluxes reaching Earth. We include in our models, for the first time for a star other than the Sun, the effect of radial particle drift due to gradients and curvatures in the stellar magnetic field. For Prox Cen we find that the inclusion of particle drift leads to less suppression of Galactic cosmic rays fluxes than when it is excluded from the model. In the case of AU Mic we explore two different wind environments, with a low and high stellar wind mass-loss rate. For AU Mic, the particle drift also leads to less suppression of the Galactic cosmic ray fluxes but it is only significant for the high mass-loss rate scenario. However, both wind scenarios for AU Mic suppress the Galactic cosmic rays strongly. Overall, careful modelling of stellar winds is needed to calculate the Galactic cosmic ray fluxes reaching exoplanets. The results found here can be used to interpret future exoplanet atmosphere observations and in atmospheric models.

10 pages, 7 figures, accepted for publication in MNRAS

References in corpus (29)

• The James Webb Space Telescope
• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• Habitable Zones Around Main-Sequence Stars: Dependence on Planetary Mass
• Habitable planets around the star Gl 581?
• Stellar magnetism: empirical trends with age and rotation
• The Structure of the Local Interstellar Medium V: Electron Densities
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• New Observational Constraints on the Winds of M Dwarf Stars
• The Space Weather of Proxima Centauri b
• New constraints on the planetary system around the young active star AU Mic. Two transiting warm Neptunes near mean-motion resonance
• Chromosphere to 1 AU Simulation of the 2011 March 7th Event: A Comprehensive Study of Coronal Mass Ejection Propagation
• Investigating the young AU~Mic system with SPIRou: large-scale stellar magnetic field and close-in planet mass
• Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic
• Magnetic cycles in a dynamo simulation of fully convective M-star Proxima Centauri
• Flares, Rotation, and Planets of the AU Mic System from TESS Observations
• The impact of coronal mass ejections and flares on the atmosphere of the hot Jupiter HD189733b
• The large-scale magnetic field of Proxima Centauri near activity maximum
• The dichotomy of atmospheric escape in AU Mic b
• MOVES IV. Modelling the influence of stellar XUV-flux, cosmic rays, and stellar energetic particles on the atmospheric composition of the hot Jupiter HD 189733b
• On the Diversity of M-Star Astrospheres and the Role of Galactic Cosmic Rays Within
• Stellar Winds and Dust Avalanches in the AU Mic Debris Disk
• The Galactic cosmic ray intensity at the evolving Earth and young exoplanets
• Stellar versus Galactic: The intensity of cosmic rays at the evolving Earth and young exoplanets around Sun-like stars
• Ariel: Enabling planetary science across light-years
• Influence of the Sun-like magnetic cycle on exoplanetary atmospheric escape
• Lightning and charge processes in brown dwarf and exoplanet atmospheres
• The Earth-like Galactic cosmic ray intensity in the habitable zone of the M dwarf GJ 436
• Charting nearby stellar systems: The intensity of Galactic cosmic rays for a sample of solar-type stars
• Galactic cosmic ray propagation through M dwarf planetary systems

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• Modeling the astrosphere of LHS~1140
• Magnetic Suppression of Cosmic Rays' Flux in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• Cosmic ray ionisation of a post-impact early Earth atmosphere: Solar cosmic ray ionisation must be considered in origin-of-life scenarios