A Simple Analytic Treatment of Partial Redistribution in Resonance Lines

It is shown that simple probabilistic approximations can help us understand partial frequency redistribution in resonance line transfer that includes Doppler diffusion. Semi-quantitative accuracy is achieved, to assist with preliminary studies or computationally challenging dynamical simulations. The purpose is to provide conceptual guidance that can improve understanding, inform computational tradeoffs, support code checking, and provide physically motivated acceleration for iterative computations.