GRMHD Simulations of Magnetized Advection Dominated Accretion on a Non-Spinning Black Hole: Role of Outflows

TL;DR

This study uses long-duration GRMHD simulations to explore how outflows behave in advection-dominated accretion onto a non-spinning black hole, revealing that outflow rates are sensitive to magnetic flux accumulation.

Contribution

First long-duration GRMHD simulations comparing magnetic flux accumulation effects on outflows in non-spinning black hole accretion.

Findings

Mass outflow rate is about 60% of inflow in flux-limited simulation.

Magnetically arrested disk reaches inflow equilibrium at larger radii.

Outflow rates are likely overestimated due to non-converged simulation times.

Abstract

We present results from two long-duration GRMHD simulations of advection-dominated accretion around a non-spinning black hole. The first simulation was designed to avoid significant accumulation of magnetic flux around the black hole. This simulation was run for a time of 200,000GM/c^3 and achieved inflow equilibrium out to a radius \sim90GM/c^2. Even at this relatively large radius, the mass outflow rate \dot{M}_{out} is found to be only 60% of the net mass inflow rate \dot{M}_{BH} into the black hole. The second simulation was designed to achieve substantial magnetic flux accumulation around the black hole in a magnetically arrested disc. This simulation was run for a shorter time of 100,000GM/c^3. Nevertheless, because the mean radial velocity was several times larger than in the first simulation, it reached inflow equilibrium out to a radius \sim170GM/c^2. Here, \dot{M}_{out} becomes equal to \dot{M}_{BH} at r\sim 160GM/c^2. Since the mass outflow rates in the two simulations do not show robust convergence with time, it is likely that the true outflow rates are lower than our estimates. The effect of black hole spin on mass outflow remains to be explored. Neither simulation shows strong evidence for convection, though a complete analysis including the effect of magnetic fields is left for the future.