Schematic representation of the magnetosphere structure: a vacuum gap of height h < r _s accelerates particles (electrons or positrons) to high Lorentz factors. The gap is exposed to soft radiation emitted from a source of size R _d . Curvature emission and inverse Compton scattering of ambient radiation produce VHE photons with a spectrum extending up to 10 ⁴ TeV. Photons having energies below a few TeV can escape freely to infinity. Interactions of IC photons having energies well above 10 TeV with the ambient radiation initiate pair cascades just above the gap, leading to a large multiplicity. A force-free outflow is established just above the pair formation front and appears as the VLBA jet. Intermittencies of the cascade process, induced by modest changes in accretion rate, give rise to the variability of the TeV emission observed by H.E.S.S., and the fluctuations of the resulted force-free outflow, as indicated by the morphological changes of the VLBA jet.