Misaligned magnetized accretion flows onto spinning black holes: Magneto-spin alignment, outflow power, and intermittent jets

TL;DR

This paper uses simulations to study how misaligned magnetic fields and black hole spins affect accretion, jet formation, and observable phenomena like flares and jet precession.

Contribution

It introduces the magneto-spin alignment mechanism and explores jet intermittency and magnetic flux dynamics in misaligned MAD systems.

Findings

Jets realign the inner disk for tilts up to 60 degrees.

Intermittent jets create hot cavities and filaments, explaining observed flares.

Large-scale misaligned flows lack sustained Lense-Thirring precession.

Abstract

Magnetic fields regulate black hole (BH) accretion, governing both inflow and outflow dynamics. When a BH accumulates substantial vertical magnetic flux, it enters the magnetically arrested disk (MAD) state, where dynamically important fields power jets and trigger disk eruptions. We investigate MAD evolution when the BH spin and disk angular momentum are misaligned, a likely scenario in many BH systems. Using numerical simulations, we show that jets from rapidly spinning, prograde BHs realign the inner disk via the magneto-spin alignment mechanism for initial tilts up to $T \lesssim 60^\circ$. Larger tilts lead to intermittent jets that disrupt the disk out to $r\gtrsim100$ gravitational radii, creating hot cavities and magnetized filaments. These episodic jets form a mini$-$feedback loop and may explain quasiperiodic X-ray and radio flares observed in low-luminosity active galaxies. We also find that (i) BH spin and disk tilt influence the amount of magnetic flux accumulated at the horizon, and (ii) large-scale, thick, misaligned accretion flows do not exhibit sustained Lense$-$Thirring (LT) precession. This suggests that slowly accreting BHs ($\dot{M} \ll 10^{-3} \dot{M}_{\rm Edd}$) are unlikely to show lightcurve quasiperiodic oscillations from LT precession, consistent with observations. Instead, magnetic flux eruptions drive jet wobbling and lateral motion, offering an alternative explanation for phenomena such as the M87 jet's apparent precession and rapid swings in blazar jet orientation.