Intrinsically Polarized Blend Lines

Abstract

The Second Solar Spectrum formed by coherent scattering processes in the Sun, is highly structured. It is characterized by numerous blend lines, both intrinsically polarizing and depolarizing, superposed on the background continuum. These blend lines play an important role in the interpretation of the Second Solar Spectrum. Since blend lines affect the shapes of the neighboring spectral lines they have to be treated in a sophisticated manner in order to efficiently model a given spectral line of interest. The depolarizing blend lines – mostly considered to be formed under LTE conditions – depolarize the background continuum and thereby affect the absolute scale of the polarization measurement. An understanding of the influence of the blend lines leads to a proper determination of the zero-point of the polarization scale. With this motivation we extend a previously developed framework to include many blend lines formed under NLTE conditions, in the radiative transfer equation. The results are shown for the particular case of two blend lines situated on either side of the main spectral line.