THOMSON SCATTERING IN A MAGNETIC-FIELD .1. FIELD ALONG ZETA

Numerical solutions to the equation of transfer are presented for the process of Thomson scattering in a constant magnetic field oriented perpendicular to a slab of electrons. These calculations are relevant to the problem of the origin of photospheric polarization in magnetic white dwarfs and scattering magnetic columns in neutron stars. The radiative transfer is done using the Monte Carlo method. Emergent intensity and polarization are presented for various atmosphere thicknesses. Some features of the emergent radiation follow: (1) The circular polarization peaks at frequencies near the cyclotron, omega-c, and for propagation direction along the field. (2) At low field strengths (high frequencies), the circular polarization is roughly proportional to omega-c/omega; the linear polarization is proportional to (omega-c/omega)2 and the amount of circular polarization present at each scatter, and is therefore much smaller than the circular polarization. (3) The linear polarization is large for propagation direction perpendicular to the magnetic field, and at frequencies near the cyclotron and in the strong-field limit (low frequencies). (4) The position angle of the linear polarization undergoes a rotation of 90-degrees at a value of omega-c/omega near square-root 3. The exact value depends on how much polarization is due to scattering symmetries when no magnetic field is present. The position angle rotation is naturally explained as a transition from the weak field to the strong field, where the preferred motion of the ion at the frequency omega changes from perpendicular to the field to parallel.