Critical temperature of white dwarfs with strong magnetic field

We calculate the pressure force by cyclotron radiation in a plane-parallel, isothermal, pure-hydrogen photosphere of a white dwarf with the dipole magnetic field taking into account correct expressions for the collision frequency in plasma on these stars. The critical temperature at which radiation pressure force per proton equals gravitational force on a magnetic white dwarf is shown to increase due to substantial decrease of the collision frequency in a strong magnetic field. This means that formation of plasma envelopes in magnetospheres of radiation-driven diskon candidates-the magnetic white dwarfs GD 229, PG 1031+/-234, and GrW+70 degrees 8247-via ejection of plasma from the star surface requires the existence of an upward temperature gradient in the photosphere.