bhlight: General Relativistic Radiation Magnetohydrodynamics with Monte Carlo Transport

TL;DR

bhlight is a novel numerical scheme that employs Monte Carlo methods to solve general relativistic radiation magnetohydrodynamics equations, enabling detailed simulations of black hole accretion flows at intermediate rates.

Contribution

It introduces a new Monte Carlo-based approach for GRRMHD, bridging the gap between radiatively efficient and inefficient accretion regimes.

Findings

Successfully tested for convergence and accuracy.

Demonstrated applications to Bondi accretion and Kerr black holes.

Provides a flexible framework for radiative GRMHD simulations.

Abstract

We present bhlight, a numerical scheme for solving the equations of general relativistic radiation magnetohydrodynamics (GRRMHD) using a direct Monte Carlo solution of the frequency-dependent radiative transport equation. bhlight is designed to evolve black hole accretion flows at intermediate accretion rate, in the regime between the classical radiatively efficient disk and the radiatively inefficient accretion flow (RIAF), in which global radiative effects play a sub-dominant but non-negligible role in disk dynamics. We describe the governing equations, numerical method, idiosyncrasies of our implementation, and a suite of test and convergence results. We also describe example applications to radiative Bondi accretion and to a slowly accreting Kerr black hole in axisymmetry.