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 pa- rameters, 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 rel- ativistic magnetohydrodynamic (GRMHD) simulations. The BZ power is dependent on the black hole spin while magnetic reconnection power is independent of it for the near force-free magnetic configuration with open field lines adopted in our theoretical study. This has obvious consequences for the time evolution of such systems particu- larly in the context of black hole X-ray binary state transitions. Our results provide analytical justification of the results obtained in GRMHD simulations.
Monthly Notices of the Royal Astronomical Society