Black hole jet power from impedance matching

Citation Penna, Robert F. "Black hole jet power from impedance matching. Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Black hole jet power depends on the angular velocity of magnetic field lines, Ω F. Force-free black hole magnetospheres typically have Ω F =Ω H ≈ 0.5, where Ω H is the angular velocity of the horizon. We give a streamlined proof of this result using an extension of the classical black hole membrane paradigm. The proof is based on an impedance-matching argument between membranes at the horizon and infinity. Then we consider a general relativistic magnetohydrodynamic simulation of an accreting, spinning black hole and jet. We find that the theory correctly describes the simulation in the jet region. However, the field lines threading the horizon near the equator have much smaller Ω F =Ω H because the force-free approximation breaks down in the accretion flow.