Radiative transfer of resonance lines with internal sources

Abstract

The modeling of resonance lines in the aurorae and dayglow usually requires a large computer code to solve the radiative transfer problem. We present here a simple theory that gives reasonable estimates of the emergent intensities, including the angular distribution, for very optically thick lines with internal sources. The method uses an extension of the H-functions (implying a semi-infinite atmosphere) and assumes that the source is monochromatic and may be reasonably represented by a Chapman profile. The theory is compared with detailed numerical calculations for resonance lines with Voigt emission line profiles, including the cases of both partial and complete frequency redistribution. The effects of frequency redistribution on the angular distribution of the emergent radiation and on the line profiles are also shown.