Physics of Pair Producing Gaps in Black Hole Magnetospheres

In some low-luminosity accreting supermassive black hole systems, the supply of plasma in the funnel region can be a problem. It is believed that a local region with an unscreened electric field can exist in the black hole magnetosphere, accelerating particles and producing high-energy gamma-rays that can create e ^± pairs. We carry out time-dependent self-consistent 1D PIC simulations of this process, including inverse-Compton scattering and photon tracking. We find a highly time-dependent solution where a macroscopic gap opens quasi-periodically to create e ^± pairs and high-energy radiation. If this gap is operating at the base of the jet in M87, we expect an intermittency on the order of a few r _g/c, which coincides with the timescale of the observed TeV flares from the same object. For Sagittarius A∗ the gap electric field can potentially grow to change the global magnetospheric structure, which may explain the lack of a radio jet at the center of our galaxy.