Radiation-Hydrodynamics Effects in an Inhomogeneous Medium

TL;DR

This paper reviews current modeling techniques for radiation transport in inhomogeneous media, presents detailed simulations of clump interactions, and evaluates the limitations of existing subgrid models in astrophysical contexts.

Contribution

It introduces new detailed simulations of radiation in inhomogeneous media and assesses the accuracy of current subgrid models used in astrophysics.

Findings

Clumps heat and expand when radiation pressure is low, reducing radiation flow.

Expanding winds from clumps can generate shocks and high-energy emissions.

Current subgrid models have limitations in accurately capturing these dynamics.

Abstract

Radiation flow through an inhomogeneous medium is critical in a wide range of physics and astronomy applications from transport across cloud layers on the earth to the propagation of supernova blast-waves producing UV and X-ray emission in supernovae. Radiation interacts with matter driving hydrodynamic feedback that further alters the radiation characteristics (energy and angular distribution). This paper reviews the current state of the art in the modeling of inhomogeneous radiation transport, subgrid models developed to capture this often-unresolved physics, and the experiments designed to improve our understanding of these models. This paper focuses on simulations based on upcoming experiments designed to test this physics. We present a series of detailed simulations (both single-clump and multi-clump conditions) probing the dependence on the physical properties of the radiation front (e.g. radiation energy) and material characteristics (specific heat, opacity, clump densities). We find that, unless the radiation pressure is high, the clumps will heat and then expand, effectively cutting off the radiation flow. The expanding winds can also produce shocks that generates high energy emission. We compare our detailed simulations with some of the current subgrid prescriptions, identifying some of the limitations of these current models.