Magnetic deformation of the white dwarf surface structure

The influence of strong, large-scale magnetic fields on the structure and t emperature distribution in white dwarf atmospheres is investigated. Magneti c fields may provide an additional component of pressure support, thus poss ibly 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 equi librium is calculated numerically in the radial direction for either for sm all deviations from different assumptions for the poloidal current distribu tion. We generally find indication that the scale height of the magnetic wh ite dwarf atmosphere enlarges with magnetic field strength and/or poloidal current strength. This is in qualitative agreement with recent spectropolar imetric observations of Grw+10 degrees 8247. Quantitatively, we find for e. g. a mean surface poloidal field strength of 100 MG and a toroidal field st rength of 2-10 MG an increase of scale height by a factor of 10. This is in dicating that already a small deviation from the initial force-free dipolar magnetic field may lead to observable effects. We further propose the meth od of finite elements for the solution of the two-dimensional magnetohydros tatic equilibrium including radiation transport in the diffusive approximat ion. We present and discuss preliminary solutions, again indicating on an e xpansion of the magnetized atmosphere.