Discrete space theory of radiative transfer

Abstract

A discrete space theory for radiative transfer based on invariant imbedding is described, along with applications. An interaction principle is defined for the relation between incident and emitted radiation from an optically thick field. A star product is used to characterize the interaction principle if other shells are present. The field at any internal point can then be quantified by selecting an appropriate number of shells and reflection and transmission operators. The internal field is expressed as a series of cells forming a two-dimensional grid over which the transfer equations can be integrated. Since the shells contain the reflection and transmission operators, combining all the cells with the star algorithm quantifies the radiation field. Sample calculations are provided for line formation in an expanding spherical stellar atmosphere.