Accuracy and Efficiency of Raytracing Photoionisation Algorithms

摘要: Three non-equilibrium photoionisation algorithms for hydrodynamical grid-based simulation codes are compared in terms of accuracy, timestepping criteria, and parallel scaling. Explicit methods with first-order time accuracy photon conservation must use very restrictive timestep criteria to accurately track R-type ionisation fronts. A second-order accurate algorithm is described which, although it requires more work per step, allows much longer timesteps consequently efficient. Implicit allow fronts cross many grid cells while maintaining accuracy. It shown, however, that errors larger multi-frequency radiation than monochromatic the implicit used here, large accrue when an front crosses optical depths a single step. The convergence rates different tested number identify best criterion each algorithm. With these selected, explicit most efficient three, its scaling significantly better upgrade from first- could be made simply fixed-grid adaptive mesh-refinement which currently method.