  Spark gaps are likely the source of plasma in active black hole (BH)
magnetospheres. In this paper, we present results of 1D general-relativistic
particle-in-cell simulations of a starved BH magnetosphere with a realistic
treatment of inverse Compton scattering and pair production, for a broad range
of conditions, run times longer than in previous studies, and different setups.
We find that following the initial discharge, the system undergoes gradual
evolution over prolonged time until either, restoring the vacuum state or
reaching a state of quasi-periodic oscillations, depending on the spectral
shape and luminosity of the ambient radiation field. The oscillations occur
near the null charge surface in cases where the global magnetospheric current
is in the direction defined by the product of the asymptotic Goldreich-Julian
charge density and the radial velocity, while they occur near the boundary of
the simulation box when it is the opposite direction (return current). Their
amplitude and the resultant luminosity of TeV photons emitted from the gap
depend sensitively on the conditions; for the cases studied here the ratio of
TeV luminosity to the Blandford-Znajek power ranges from $10^{-5}$ to
$10^{-2}$, suggesting that strong flares may be generated by moderate changes
in disk emission. We also examined the dependence of the solution on the
initial number of particles per cell (PPC) and found convergence for PPC of
about 50 for the cases examined. At lower PPC values the pair multiplicity is
found to be artificially high, affecting the solution considerably.
