Bremsstrahlung of Waves Polarized Linearly Across a Strong Magnetic Field in Low-Energy Electron–Nucleus Collisions

We analyze bremsstrahlung which accompanies the low-energy electron–nucleus collisions in a strong magnetic field under the condition that the electron Larmor radius is less than the characteristic impact parameter of close Coulomb collisions in the absence of the magnetic field. We calculate the spectral emissive power at frequencies below the electron cyclotron frequency, which is stipulated by the electric drift of the electron gyration axis in the Coulomb field of a nucleus and the external magnetic field. The electric drift produces the nonzero bremsstrahlung and collisional absorption of linearly polarized waves transverse to an external magnetic field. We show that in thermal equilibrium the absorption coefficient of the extraordinary waves in a rarefied plasma reaches a minimum at the corresponding frequency. The minimum can ensure that these waves exit from the deeper and hotter layers in the photosphere of an isolated magnetic white dwarf compared with the ordinary waves. This effect can stipulate the observed linear polarization of the star emission in the band below the electron cyclotron frequency.