Gralla, Samuel E.Lupsasca, AlexandruStrominger, Andrew2016-11-082016Gralla, Samuel E., Alexandru Lupsasca, and Andrew Strominger. 2016. “Near-Horizon Kerr Magnetosphere.” Phys. Rev. D 93 (10) (May 23). doi:10.1103/physrevd.93.104041.2470-0010http://nrs.harvard.edu/urn-3:HUL.InstRepos:29374521We exploit the near-horizon conformal symmetry of rapidly spinning black holes to determine universal properties of their magnetospheres. Analytic expressions are derived for the limiting form of the magnetosphere in the near-horizon region. The symmetry is shown to imply that the black hole Meissner effect holds for free Maxwell fields but is generically violated for force-free fields. We further show that in the extremal limit, near-horizon plasma particles are infinitely boosted relative to accretion flow. Active galactic nuclei powered by rapidly spinning black holes are therefore natural sites for high-energy particle collisions.en-USJournal Article2016-11-0810.1103/PhysRevD.93.104041