  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 unscreened electric field can exist in the black hole
magnetosphere, accelerating particles and producing high energy gamma-rays that
can create $e^{\pm}$ 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 $e^{\pm}$ 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 time
scale 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.
