GRMHD Simulations of Magnetized Accretion Disk/Jet: Variabilities of Black Holes and Spectral Energy Distributions in Magnetic States

TL;DR

This study uses 3D GRMHD simulations to explore how magnetic flux states in accretion disks around spinning black holes influence jet efficiency, spectral energy distributions, and variability, linking these to observable phenomena.

Contribution

It systematically investigates the connection between magnetic flux states and observable properties in black hole accretion, introducing diagnostics that relate simulation dynamics to multiwavelength observations.

Findings

MAD states produce the highest radiative luminosity and variability.

INT states show moderate variability driven by episodic reconnection.

SANE states exhibit stochastic MRI turbulence with lower variability.

Abstract

We perform three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of a near-maximally spinning black hole (spin parameter, a = 0.998) with varying initial magnetic field geometries, systematically exploring the parameter space connecting magnetically arrested disk (MAD), intermediate (INT), and standard and normal evolution (SANE) accretion states. The magnetic flux threading the black hole horizon emerges as the fundamental state variable controlling jet efficiency, flow magnetization, and radiative output across all three states. We introduce complementary diagnostics-broadband spectral energy distributions spanning radio through hard X-ray frequencies and time-resolved X-ray light curves-that together connect simulation dynamics directly to multiwavelength observables. The radiative output follows a clear MAD > INT > SANE hierarchy in time-averaged luminosity, mean X-ray emission, as well as variability. Furthermore, MAD exhibits the highest fractional variability through quasi-periodic magnetic flux eruption events, and INT and SANE show moderate variability driven by episodic reconnection and stochastic MRI turbulence, respectively. Scaling to GRS 1915+105, Cyg X-1, and HLX-1, we demonstrate that all twelve temporal classes of GRS 1915+105 map naturally onto our three magnetic states, Cyg X-1's persistent hard state is reproduced by a sustained INT configuration, and HLX-1's extreme luminosities arise through efficient Blandford-Znajek extraction in MAD states scaled to higher black hole mass.