At a fundamental level, the radiation can be described by the time evolution of the spectral radiation intensity I ν( r, t, n, ν), which is the radiation energy per unit area, per unit solid angle in the direction of photon propagation n, per unit interval of photon frequency ν, per unit time interval.

At high enough energy density the radiation heats and accelerates the plasma. Both CRASH and BATS-R-US are part of the publicly available Space Weather Modeling Framework.Īs photons travel through matter, the radiation field experiences changes due to net total emission, absorption, and scattering see, for instance, Mihalas & Mihalas ( 1984), Pomraming ( 2005), and Drake ( 2006).

The CRASH code is an extension of the Block-Adaptive Tree Solarwind Roe Upwind Scheme (BATS-R-US) code with a new radiation transfer and heat conduction library and equation-of-state and multi-group opacity solvers. The applications are for astrophysics and laboratory astrophysics. We present a suite of verification test problems to demonstrate the accuracy and performance of the algorithms. An operator-split method is used to solve these equations in three substeps: (1) an explicit step of a shock-capturing hydrodynamic solver (2) a linear advection of the radiation in frequency-logarithm space and (3) an implicit solution of the stiff radiation diffusion, heat conduction, and energy exchange. The radiation hydrodynamic equations are solved in the Eulerian frame by means of a conservative finite-volume discretization in either one-, two-, or three-dimensional slab geometry or in two-dimensional cylindrical symmetry. Electrons and ions are allowed to have different temperatures and we include flux-limited electron heat conduction. The implementation solves the radiation diffusion model with a gray or multi-group method and uses a flux-limited diffusion approximation to recover the free-streaming limit. We describe the Center for Radiative Shock Hydrodynamics (CRASH) code, a block-adaptive-mesh code for multi-material radiation hydrodynamics.

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