Global trends in winds of M dwarf stars

Abstract

M dwarf stars are currently the main targets in searches for potentially habitable planets. However, their winds have been suggested to be harmful to planetary atmospheres. Here, in order to better understand the winds of M dwarfs and also infer their physical properties, we perform a one-dimensional magnetohydrodynamic parametric study of winds of M dwarfs that are heated by dissipation of Alfvén waves. These waves are triggered by sub-surface convective motions and propagate along magnetic field lines. Here, we vary the magnetic field strength and density at the wind base (chromosphere), while keeping the same relative wave amplitude ($0.1B_0$) and dissipation lenghtscale. We find that our winds very quickly reach isothermal temperatures with mass-loss rates proportional to base density square. We compare our results with Parker wind models and find that, in the high-beta regime, both models agree. However, in the low-beta regime, the Parker wind underestimates the terminal velocity by around one order of magnitude and mass-loss rate by several orders of magnitude. We also find that M dwarfs could have chromospheres extending to 18% to 180% of the stellar radius. We apply our model to the planet-hosting star GJ 436 and find, from X-ray observational constraints, $\dot{M}<7.6\times 10^{-15}{M}_{\odot }{\text{yr}}^{-1}$. This is in agreement with values derived from the Lyman-alpha transit of GJ 436b, indicating that spectroscopic planetary transits could be used as a way to study stellar wind properties.

12 pages, 11 figures

References in corpus (12)

• Habitable planets around the star Gl 581?
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• Large-scale magnetic topologies of late M dwarfs
• The Mass-Dependence of Angular Momentum Evolution in Sun-Like Stars
• The Space Weather of Proxima Centauri b
• Magnetic fields in M dwarfs from the CARMENES survey
• Estimating magnetic filling factors from Zeeman-Doppler magnetograms
• Global 3D hydrodynamic modeling of in-transit Lyα absorption of GJ436b
• Exoplanets as probes of the winds of host stars: the case of the M dwarf GJ 436
• Radio emission and mass loss rate limits of four young solar-type stars
• A Comparison Between Physics-based and Polytropic MHD Models for Stellar Coronae and Stellar Winds of Solar Analogs
• Transit Ly-$\alpha$ signatures of terrestrial planets in the habitable zones of M dwarfs

Cited by in corpus (15)

• New Observational Constraints on the Winds of M Dwarf Stars
• The evolution of the solar wind
• Stellar wind effects on the atmospheres of close-in giants: a possible reduction in escape instead of increased erosion
• The large-scale magnetic field of Proxima Centauri near activity maximum
• GJ 436b and the stellar wind interaction: simulations constraints using Ly$\alpha$ and H$\alpha$ transits
• The space weather around the exoplanet GJ 436 b. II. Stellar wind-exoplanet interactions
• The Earth-like Galactic cosmic ray intensity in the habitable zone of the M dwarf GJ 436
• M-dwarf's Chromosphere, Corona and Wind Connection via the Nonlinear Alfvén Wave
• The energetic particle environment of a GJ 436 b-like planet
• Impact of M-dwarf Stellar Wind and Photoevaporation on the Atmospheric Evolution of Small Planets
• Nonlinear Alfvén Wave Model of Stellar Coronae and Winds from the Sun to M dwarfs
• Galactic cosmic ray propagation through M dwarf planetary systems
• Infrared-Radio-follow-up Observations for Detection of the Magnetic Radio Emission of Extra-Solar Planets: A New Window to Detect Exoplanets
• Measurement of stellar and substellar winds using white dwarf hosts
• The impact of stellar winds and tidal locking effects on the habitability of Earth-like exoplanets around M dwarf stars