The Effect of Collisions on Spectral Line Formation in Solar Magnetic Regions

Abstract

The present paper describes the results of a preliminary investigation of the effects on the absorption, emission, and scattering of polarized light caused by collisions between the atoms of interest and surrounding perturbers under physical conditions typical of solar magnetic regions. The description of these effects in terms of atomic level polarization is reviewed and the processes which can lead to atomic level polarization in solar magnetic regions and those which tend to reduce it are summarized. The effects associated with collisional relaxation of atomic level polarization are discussed and a method for estimating relaxation rates is described. Estimates of collisional relaxation rates are used to calculate upper limits on the degree of polarization of the levels involved in the formation of five magnetically-sensitive FeI absorption lines. The implications of the results for the form of radiative transfer equations used to describe the formation of these lines are discussed.