On a transition from solar-like coronae to rotation-dominated jovian-like magnetospheres in ultracool main-sequence stars

Abstract

For main-sequence stars beyond spectral type M5 the characteristics of magnetic activity common to warmer solar-like stars change into the brown-dwarf domain: the surface magnetic field becomes more dipolar and the evolution of the field patterns slows, the photospheric plasma is increasingly neutral and decoupled from the magnetic field, chromospheric and coronal emissions weaken markedly, and the efficiency of rotational braking rapidly decreases. Yet, radio emission persists, and has been argued to be dominated by electron-cyclotron maser emission instead of the gyrosynchrotron emission from warmer stars. These properties may signal a transition in the stellar extended atmosphere. Stars warmer than about M5 have a solar-like corona and wind-sustained heliosphere in which the atmospheric activity is powered by convective motions that move the magnetic field. Stars cooler than early-L, in contrast, may have a jovian-like rotation-dominated magnetosphere powered by the star's rotation in a scaled-up analog of the magnetospheres of Jupiter and Saturn. A dimensional scaling relationship for rotation-dominated magnetospheres by Fan et al. (1982) is consistent with this hypothesis.

References in corpus (13)

• Large-scale magnetic topologies of early M dwarfs
• The First Direct Measurements of Magnetic Fields on Very Low-Mass Stars
• Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
• Activity and Kinematics of Ultracool Dwarfs Including An Amazing Flare Observation
• Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM 513-46546: Broadband Coherent Emission at the Substellar Boundary?
• On the magnetic topology of partially and fully convective stars
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. II. Mixed Trends in VB10 and LSR1835+32 and the Possible Role of Rotation
• A Chandra X-ray detection of the L dwarf binary Kelu-1: Simultaneous Chandra and Very Large Array observations
• Quiescent X-ray emission from the M9 dwarf LHS 2065
• Ultra-Cool and Extra-Vigorous: Rotation and Activity in M and L dwarfs

Cited by in corpus (24)

• Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
• A Panchromatic View of Brown Dwarf Aurorae
• Origin of electron cyclotron maser-induced radio emissions at ultra-cool dwarfs: magnetosphere-ionosphere coupling currents
• A Survey for H-alpha Emission from Late L dwarfs and T dwarfs
• A scaling relationship for non-thermal radio emission from ordered magnetospheres: from the top of the Main Sequence to planets
• Volume-limited radio survey of ultracool dwarfs
• Low-frequency monitoring of flare star binary CR Draconis: Long-term electron-cyclotron maser emission
• A Search for Photometric Variability in L and T type Brown Dwarf Atmospheres
• Radio Flaring from the T6 Dwarf WISEPC J112254.73+255021.5 with A Possible Ultra-short Periodicity
• The Hyperactive L Dwarf 2MASS J13153094-2649513: Continued Emission and a Brown Dwarf Companion
• Variable and polarized radio emission from the T6 brown dwarf WISEP J112254.73+255021.5
• Auroral Radio Emission from Ultracool Dwarfs: a Jovian Model
• Comparative analysis of two formation scenarios of bursty radio emission from ultracool dwarfs
• Detection of Radio Emission from the Hyperactive L Dwarf 2MASS J13153094-2649513AB
• Periodic Radio Emission from the T8 Dwarf WISE J062309.94-045624.6
• Radio-flaring Ultracool Dwarf Population Synthesis
• A Deep Radio Limit for the TRAPPIST-1 System
• The UV spectrum of the Ultracool Dwarf LSR J1835+3259 observed with the Hubble Space Telescope
• Multi-Epoch VLBI of L Dwarf Binary 2MASS J0746+2000AB: Precise Mass Measurements and Confirmation of Radio Emission from Both Components
• Radio Emission from Ultra-Cool Dwarfs
• Flash ionisation signature in coherent cyclotron emission from Brown Dwarfs
• Measurement of stellar and substellar winds using white dwarf hosts
• ROME IV. The Arecibo Search for Substellar Magnetospheric Radio Emissions in Purported Exoplanet-Hosting Systems at 5 GHz
• Radio Emission from UV Cet: Auroral Emission from a Stellar Magnetosphere