Extreme magnetic fields around black holes

TL;DR

This paper reviews recent advances in understanding magnetic fields around black holes, especially in magnetically arrested disks, highlighting their role in jet formation, feedback mechanisms, and potential observational signatures.

Contribution

It provides an overview of magnetic field evolution in simulations of accreting black holes, emphasizing jet launching, feedback, and imaging prospects of MADs.

Findings

Misaligned MADs show jet ejection cycles that may cause flaring in radio-quiet AGNs.

Advances in horizon-scale imaging could detect disk misalignment through the disk-jet connection.

Magnetic fields are crucial in black hole accretion and jet physics, as revealed by recent simulations and observations.

Abstract

Recent results of the event horizon-scale images of M87* and Sagittarius A* from the Event Horizon Telescope Collaboration show that strong magnetic fields are likely present around the central black holes (BHs) in these sources. Magnetically arrested disks (MADs), the end stage of magnetic flux saturation around BHs, are especially rich in horizon-scale physics due to the presence of powerful jets and magnetic flux eruptions that provide significant feedback on the accretion mechanism. Here, we present an overview of our current knowledge about the magnetic field evolution in numerical simulations of accreting BHs, focusing on jet launching, black hole-interstellar medium feedback, and black hole imaging of MADs. We find that misaligned MAD accretion flows seemingly exhibit jet ejection cycles that could produce flaring states in radio-quiet active galactic nuclei. Further, we show that advances in horizon-scale interferometric telescopes could identify disk misalignment by imaging the disk-jet connection region.