Small-scale magnetic fields on late-type M-dwarfs
(2002) In Astronomical Notes - Astronomische Nachrichten 323(3-4). p.402-406- Abstract
- We performed kinematic studies of the evolution of small-scale magneticfields in the surface layers of M-dwarfs. We solved the inductionequation for a prescribed velocity field, magnetic Reynolds number ReM,and boundary conditions in a Cartesian box, representing a volumecomprising the optically thin stellar atmosphere and the uppermost partof the optically thick convective envelope. The velocity field isspatially and temporally variable, and stems from detailedradiation-hydrodynamics simulations of convective flows in aproto-typical late-type M-dwarf (Teff =2800pun {K}, logg =5.0, solarchemical composition, spectral type ~M6). We find dynamo action for ReM>= 400. Growth time scales of the magnetic field are comparable tothe convective... (More)
- We performed kinematic studies of the evolution of small-scale magneticfields in the surface layers of M-dwarfs. We solved the inductionequation for a prescribed velocity field, magnetic Reynolds number ReM,and boundary conditions in a Cartesian box, representing a volumecomprising the optically thin stellar atmosphere and the uppermost partof the optically thick convective envelope. The velocity field isspatially and temporally variable, and stems from detailedradiation-hydrodynamics simulations of convective flows in aproto-typical late-type M-dwarf (Teff =2800pun {K}, logg =5.0, solarchemical composition, spectral type ~M6). We find dynamo action for ReM>= 400. Growth time scales of the magnetic field are comparable tothe convective turn-over time scale (~ 150pun {sec}). The convectivevelocity field concentrates the magnetic field in sheets and tubularstructures in the inter-granular downflows. Scaling from solarconditions suggests that field strengths as high as 20pun{kG} might bereached locally. Perhaps surprisingly, ReM is of order unity in thesurface layers of cooler M-dwarfs, rendering the dynamo inoperative. Inall studied cases we find a rather low spatial filling factor of themagnetic field. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/130338
- author
- Dorch, S B F and Ludwig, Hans-Günter LU
- organization
- publishing date
- 2002
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- stars: activity, stars: low-mass, stars: magnetic fields
- in
- Astronomical Notes - Astronomische Nachrichten
- volume
- 323
- issue
- 3-4
- pages
- 402 - 406
- publisher
- John Wiley & Sons Inc.
- external identifiers
-
- wos:000177865100044
- scopus:0036398779
- ISSN
- 0004-6337
- DOI
- 10.1002/1521-3994(200208)323:3/4<402::AID-ASNA402>3.0.CO;2-H
- language
- English
- LU publication?
- yes
- id
- aebaf2d5-ff18-44a5-a139-a661698cf173 (old id 130338)
- date added to LUP
- 2016-04-01 12:28:32
- date last changed
- 2024-01-08 21:46:44
@article{aebaf2d5-ff18-44a5-a139-a661698cf173,
abstract = {{We performed kinematic studies of the evolution of small-scale magneticfields in the surface layers of M-dwarfs. We solved the inductionequation for a prescribed velocity field, magnetic Reynolds number ReM,and boundary conditions in a Cartesian box, representing a volumecomprising the optically thin stellar atmosphere and the uppermost partof the optically thick convective envelope. The velocity field isspatially and temporally variable, and stems from detailedradiation-hydrodynamics simulations of convective flows in aproto-typical late-type M-dwarf (Teff =2800pun {K}, logg =5.0, solarchemical composition, spectral type ~M6). We find dynamo action for ReM>= 400. Growth time scales of the magnetic field are comparable tothe convective turn-over time scale (~ 150pun {sec}). The convectivevelocity field concentrates the magnetic field in sheets and tubularstructures in the inter-granular downflows. Scaling from solarconditions suggests that field strengths as high as 20pun{kG} might bereached locally. Perhaps surprisingly, ReM is of order unity in thesurface layers of cooler M-dwarfs, rendering the dynamo inoperative. Inall studied cases we find a rather low spatial filling factor of themagnetic field.}},
author = {{Dorch, S B F and Ludwig, Hans-Günter}},
issn = {{0004-6337}},
keywords = {{stars: activity; stars: low-mass; stars: magnetic fields}},
language = {{eng}},
number = {{3-4}},
pages = {{402--406}},
publisher = {{John Wiley & Sons Inc.}},
series = {{Astronomical Notes - Astronomische Nachrichten}},
title = {{Small-scale magnetic fields on late-type M-dwarfs}},
url = {{http://dx.doi.org/10.1002/1521-3994(200208)323:3/4<402::AID-ASNA402>3.0.CO;2-H}},
doi = {{10.1002/1521-3994(200208)323:3/4<402::AID-ASNA402>3.0.CO;2-H}},
volume = {{323}},
year = {{2002}},
}