A study of the MAD accretion state across black hole spins for radiatively inefficient accretion flows

TL;DR

This paper presents GRMHD simulations exploring how black hole spin influences the properties of Magnetically Arrested Disks and their jets, revealing complex, spin-dependent behaviors in accretion and jet dynamics.

Contribution

The study provides new insights into the impact of black hole spin on MAD accretion flows and jet characteristics through comprehensive simulations across various spins.

Findings

High positive spin enhances angular momentum transport via jets.

Mass accretion rate and MAD parameter are anti-correlated in their derivatives.

Jet width and fluctuations vary significantly with black hole spin.

Abstract

The study of Magnetically Arrested Disks (MAD) attract strong interest in recent years, as these disk configurations were found to generate strong jets as observed in many accreting systems. Here, we present the results of 14 general relativistic magnetohydrodynamic(GRMHD) simulations of advection dominated accretion flow in the MAD state across black hole spins, carried with cuHARM. Our main findings are as follows. (i) The jets transport a significant amount of angular momentum to infinity in the form of Maxwell stresses. For positive, high spin, the rate of angular momentum transport is about 5 times larger than for negative spin. This contribution is nearly absent for a non-rotating black hole. (ii) The mass accretion rate and the MAD parameter, both calculated at the horizon, are not correlated. However, their time derivatives are anti-correlated for every spin. (iii) For zero spin, the contribution of the toroidal component of the magnetic field to the magnetic pressure is negligible, while for fast spinning black hole, it is in the same order as the contribution of the radial magnetic component. For high positive spin, the toroidal component even dominates. (iv) For negative spins, the jets are narrower than their positive spin counterparts, while their fluctuations are larger. The weak jet from the non-rotating black hole is the widest with the smallest fluctuations. Our results highlight the complex, non-linear connection between the black hole spin and the resulting disk and jet properties in the MAD regime.