Electron Scattering Redistribution Effect on Atomic Line Polarization

Abstract

The scattering of line photons on free electrons modifies the polarization of the atomic spectral lines. Hence it is important to treat scattering by electrons as a redistribution process and to study in detail its effect on line formation. The numerically difficult problem of evaluation and the use of angle-dependent atomic and electron scattering redistribution functions in the line transfer equation is considered. Two numerical methods, namely approximate lambda iteration and scattering expansion method, are used to solve the relevant polarized transfer problem. A study of the polarized line formation in a standard two-level atom picture including an exact treatment of electron scattering redistribution shows the importance of the latter in the analysis of polarized line profiles emitted by solar and stellar atmospheres. The effect of electron scattering turns out to be extremely important in the interpretation of very far wing line polarization of solar and stellar spectral lines.