Towards understanding dynamo action in M dwarfs

Abstract

Recent progress in observational studies of magnetic activity in M dwarfs urgently requires support from ideas of stellar dynamo theory. We propose a strategy to connect observational and theoretical studies. In particular, we suggest four magnetic configurations that appear relevant to dwarfs from the viewpoint of the most conservative version of dynamo theory, and discuss observational tests to identify the configurations observationally. As expected, any such identification contains substantial uncertainties. However the situation in general looks less pessimistic than might be expected. Several identifications between the phenomenology of individual stars and dynamo models are suggested. Remarkably, all models discussed predict substantial surface magnetic activity at rather high stellar latitudes. This prediction looks unexpected from the viewpoint of our experience observing the Sun (which of course differs in some fundamental ways from these late-type dwarfs). We stress that a fuller understanding of the topic requires a long-term (at least 15 years) monitoring of M dwarfs by Zeeman-Doppler imaging.

8 pages, 4 figures, accepted by MNRAS

References in corpus (11)

• Large-scale magnetic topologies of late M dwarfs
• Stellar magnetism: empirical trends with age and rotation
• Simulations of dynamo action in fully convective stars
• Large-scale magnetic topologies of early M dwarfs
• Magnetic field generation in fully convective rotating spheres
• The large-scale axisymmetric magnetic topology of avery-low-mass fully-convective star
• Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
• Turbulent magnetic Prandtl number and magnetic diffusivity quenching from simulations
• Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars
• The new HiVIS spectropolarimeter and spectropolarimetric calibration of the AEOS telescope
• Spectropolarimetric observations of Herbig Ae/Be Stars I: HiVIS spectropolarimetric calibration and reduction techniques

Cited by in corpus (5)

• Strong dipole magnetic fields in fast rotating fully convective stars
• Magnetic cycles in a dynamo simulation of fully convective M-star Proxima Centauri
• Surprisingly different starspot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
• Nonlinear regimes in mean-field full-sphere dynamo
• Modelling the environment around five ultracool dwarfs via the radio domain