FRONTIERS IN COMPUTATIONAL ASTROPHYSICS

Particle and Flames in Radiative and Magnetic Flows

October 11-15, 2010
Lyon, France

Contribution of Rolf Kuiper

Title

Ray-tracing + Flux-Limited-Diffusion: A hybrid method for fast and accurate frequency-dependent radiation transport in MHD simulations

Topics

"Stellar structure and evolution"

Keywords

radiation transport, Flux-Limited-Diffusion, ray-tracing, frequency dependence

Abstract

Flux-Limited-Diffusion is still the default method for radiation transport in (M)HD simulations. The method is unreliable in transition regions from optically thick to optically thin (e.g. disk atmospheres) and the extension to frequency-dependent radiation transport results in a dramatic increase of cpu time usage. Both of these issues can be solved for problems including a dominant central source of radiation energy (e.g. a single star or AGN) by solving the irradiation of this source in a frequency-dependent ray-tracing step. Re-emission of the irradiated regions can afterwards be shifted to a standard gray FLD-solver. We will present the numerical scheme of this hybrid method we implemented into our version of the MHD code Pluto and demonstrate its validity in a dedicated radiation benchmark test problems for Monte-Carlo and ray-tracing methods (Kuiper et al. 2010). The module was already successfully applied to the radiation pressure problem in the formation of massive stars.

Talk