THE F-N METHOD FOR SPECTRAL-LINE FORMATION BY COMPLETELY NONCOHERENT SCATTERING

The F-N method is used to develop a solution to a class of nongrey pro blems in the theory of radiative transfer. The model considered allows for scattering with complete frequency redistribution (completely non coherent scattering) and continuum absorption. In addition to a genera l formulation, a specific solution is developed for an inhomogeneous s ource term (Planck function) that varies linearly with optical depth i n a semi-infinite medium. Test problems based on Doppler and Lorentz p rofiles of the line-scattering coefficient are considered, and numeric al results (thought to be correct to five significant figures) are giv en for the frequency-dependent intensity exiting the medium and for th e source function within the medium. For comparison purposes, a previo usly reported solution that is expressed in terms of Chandrasekhar's H function is evaluated numerically. (C) 1998 Elsevier Science Ltd. All rights reserved.