Magnetic Reconnection Heating of Thin Accretion Disks around Kerr Black Holes

Abstract

The magnetic reconnection process near a black hole can efficiently convert magnetic energy into the kinetic and thermal energy of plasma outflows, enabling the extraction of rotational energy from a spinning black hole. However, its impact on the surrounding accretion disk remains insufficiently explored. In this work, we develop a framework to investigate the 'heating' effect of magnetic reconnection outflow plasma on thin accretion disks around Kerr black holes. We incorporate the energy and angular momentum fluxes of reconnection outflow into the disk conservation laws as additional source terms, yielding a modified radiative flux. We investigate the dependence of the modified radiative flux on the black hole spin, reconnection radius, plasma magnetization, and outflow orientation. For a fixed magnetic field prescription, the contribution of the reconnection outflow plasma to the modified radiative flux decreases as the black hole spin increases. Its dependence on the reconnection radius differs inside and outside the ergosphere: inside, a smaller radius enhances disk heating through more efficient extraction of black hole rotational energy, whereas outside, a larger radius produces stronger heating due to reduced radial dilution of the outflow. The reconnection outflow plasma contribution also increases with plasma magnetization and the radial component of the outflow velocity. Our results demonstrate that magnetic reconnection can provide an additional source of energy and angular momentum for relativistic accretion disks, establishing a connection between plasma processes near rotating black holes and the observable accretion disk properties, providing a new perspective on the strong gravitational field regime.