Magnetocentrifugal launching of jets from disks around Kerr black holes

TL;DR

This paper investigates how strong magnetic fields enable jet launching from accretion disks around Kerr black holes, revealing that black hole spin influences the magnetic angle conditions for jet formation.

Contribution

It extends the understanding of magnetocentrifugal jet launching to Kerr black holes, showing how black hole spin affects magnetic field angles needed for jet ejection.

Findings

Magnetocentrifugal launching angle is less than 60° for Schwarzschild black holes.

The angle increases with black hole spin, reaching 90° near the horizon of a maximally spinning black hole.

A critically spinning black hole can launch jets along the rotation axis.

Abstract

Strong magnetic fields modify particle motion in the curved space-time of spinning black holes and change the stability conditions of circular orbits. We study conditions for magnetocentrifugal jet launching from accretion disks around black holes, whereby large scale black hole lines anchored in the disk may fling tenuous coronal gas outward. For a Schwarzschild black hole, magnetocentrifugal launching requires that the poloidal component of magnetic fields makes an angle less than $60^\circ$ to the outward direction at the disk surface, similar to the Newtonian case. For prograde rotating disks around Kerr black holes, this angle increases and becomes $90^\circ$ for footpoints anchored to the disk near the horizon of a critically spinning $a=M$ black hole. Thus, a disk around a critically spinning black hole may centrifugally launch a jet even along the rotation axis.