Magnetic reconnection and Blandford-Znajek process around rotating black holes

TL;DR

This paper compares the magnetic reconnection power and Blandford-Znajek power around rotating black holes, showing reconnection can rival BZ power under realistic conditions, with implications for black hole systems.

Contribution

It provides a semi-analytic comparison between reconnection and BZ powers, highlighting conditions where reconnection may dominate in rotating black hole environments.

Findings

Reconnection power can compete with BZ power for realistic parameters.

BZ power depends on black hole spin, reconnection power does not.

Results support previous GRMHD simulation findings.

Abstract

We provide a semi-analytic comparison between the Blandford-Znajek (BZ) and the magnetic reconnection power for accreting black holes in the curved spacetime of a rotating black hole. Our main result is that for a realistic range of astrophysical parameters, the reconnection power may compete with the BZ power. The field lines anchored close to or on the black hole usually evolve to open field lines in general relativistic magnetohydrodynamic (GRMHD) simulations. The BZ power is dependent on the black hole spin while magnetic reconnection power is independent of it for the force-free magnetic configuration with open field lines adopted in our theoretical study. This has obvious consequences for the time evolution of such systems particularly in the context of black hole X-ray binary state transitions. Our results provide analytical justification of the results obtained in GRMHD simulations.