Radiative Transfer in Anisotropic Scattering Media

Transfer and moment equations in anisotropic scattering media are formulated under a simple linear model using the Eddington approximation. In the transfer equation, a term including the radiative flux appears, and the first moment equation is also modified, while the zeroth moment equation does not change, since the scattering processes exchange momentum, but not energy. Moment equations and transfer equation are solved for several simple cases to clarify the qualitative properties of radiative transfer in anisotropic scattering media. When forward scattering dominates, the radiative intensity is enhanced in some cases, while the gradient of the mean intensity decreases in other cases, depending on the boundary conditions for the problem. These analytic expressions are helpful in studying and understanding the radiative properties of stars with dusty envelopes, interstellar matter, protoplanetary disks and star forming regions, and the dusty universe.