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Magnetic deformation of the white dwarf surface structure

Fendt, Ch and Dravins, D. LU (2000) In Astronomische Nachrichten 321(3). p.193-206
Abstract

The influence of strong, large-scale magnetic fields on the structure and temperature distribution in white dwarf atmospheres is investigated. Magnetic fields may provide an additional component of pressure support, thus possibly inflating the atmosphere compared to the non-magnetic case. Since the magnetic forces are not isotropic, atmospheric properties may significantly deviate from spherical symmetry. In this paper the magnetohydrostatic equilibrium is calculated numerically in the radial direction for either for small deviations from different assumptions for the poloidal current distribution. We generally find indication that the scale height of the magnetic white dwarf atmosphere enlarges with magnetic field strength and/or... (More)

The influence of strong, large-scale magnetic fields on the structure and temperature distribution in white dwarf atmospheres is investigated. Magnetic fields may provide an additional component of pressure support, thus possibly inflating the atmosphere compared to the non-magnetic case. Since the magnetic forces are not isotropic, atmospheric properties may significantly deviate from spherical symmetry. In this paper the magnetohydrostatic equilibrium is calculated numerically in the radial direction for either for small deviations from different assumptions for the poloidal current distribution. We generally find indication that the scale height of the magnetic white dwarf atmosphere enlarges with magnetic field strength and/or poloidal current strength. This is in qualitative agreement with recent spectropolarimetric observations of Grw+10°8247. Quantitatively, we find for e.g. a mean surface poloidal field strength of 100 MG and a toroidal field strength of 2-10 MG an increase of scale height by a factor of 10. This is indicating that already a small deviation from the initial force-free dipolar magnetic field may lead to observable effects. We further propose the method of finite elements for the solution of the two-dimensional magnetohydrostatic equilibrium including radiation transport in the diffusive approximation. We present and discuss preliminary solutions, again indicating on an expansion of the magnetized atmosphere.

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author
organization
publishing date
type
Contribution to journal
publication status
published
keywords
Fundamental parameters, Magnetic fields, Stars: Atmospheres, White dwarfs
in
Astronomische Nachrichten
volume
321
issue
3
pages
14 pages
publisher
John Wiley & Sons
external identifiers
  • scopus:0034353958
ISSN
0004-6337
language
English
LU publication?
yes
id
aaf670a2-7944-4e7d-bca4-d25566dd3b2f
date added to LUP
2017-11-22 15:22:43
date last changed
2018-05-29 10:35:03
@article{aaf670a2-7944-4e7d-bca4-d25566dd3b2f,
  abstract     = {<p>The influence of strong, large-scale magnetic fields on the structure and temperature distribution in white dwarf atmospheres is investigated. Magnetic fields may provide an additional component of pressure support, thus possibly inflating the atmosphere compared to the non-magnetic case. Since the magnetic forces are not isotropic, atmospheric properties may significantly deviate from spherical symmetry. In this paper the magnetohydrostatic equilibrium is calculated numerically in the radial direction for either for small deviations from different assumptions for the poloidal current distribution. We generally find indication that the scale height of the magnetic white dwarf atmosphere enlarges with magnetic field strength and/or poloidal current strength. This is in qualitative agreement with recent spectropolarimetric observations of Grw+10°8247. Quantitatively, we find for e.g. a mean surface poloidal field strength of 100 MG and a toroidal field strength of 2-10 MG an increase of scale height by a factor of 10. This is indicating that already a small deviation from the initial force-free dipolar magnetic field may lead to observable effects. We further propose the method of finite elements for the solution of the two-dimensional magnetohydrostatic equilibrium including radiation transport in the diffusive approximation. We present and discuss preliminary solutions, again indicating on an expansion of the magnetized atmosphere.</p>},
  author       = {Fendt, Ch and Dravins, D.},
  issn         = {0004-6337},
  keyword      = {Fundamental parameters,Magnetic fields,Stars: Atmospheres,White dwarfs},
  language     = {eng},
  number       = {3},
  pages        = {193--206},
  publisher    = {John Wiley & Sons},
  series       = {Astronomische Nachrichten},
  title        = {Magnetic deformation of the white dwarf surface structure},
  volume       = {321},
  year         = {2000},
}