GRMHD simulations of magnetized advection-dominated accretion on a non-spinning black hole: role of outflows

We present results from two long-duration general relativistic magneto-hydrodynamic (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 200 000 GM/c(3) and achieved inflow equilibrium out to a radius similar to 90 GM/c(2). Even at this relatively large radius, the mass outflow rate (M) over dot(out) is found to be only 60 per cent of the net mass inflow rate (M) over dot(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 100 000 GM/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 similar to 170 GM/c(2). Here, (M) over dot(out) becomes equal to (M) over dot(BH) at r similar to 160 GM/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.