Plasma production around spinning supermassive black holes

It is believed that rapidly spinning, supermassive black holes (BH) exist in centers of Active Galactic Nuclei and produce powerful relativistic jets via the Blandford-Znajek (BZ) mechanism. The BZ process, which taps the BH spin energy the electromagnetic Poynting flux, requires the presence of plasma to carry current. Since the BHs possess both inner and outer light cylinders, the magnetospheric plasma escapes on a dynamical time scale. Thus, it must be replenished. Previous studies indicate that the plasma is created and replenished in situ via an electron-positron cascade. Here we discuss the cascade mechanism and present the results of the numerical solutions of the system of coupled ODEs describing the particle and photon fluxes. While this semi-analytical study has some limitations, it allows one to explore important scaling relations between the plasma and astrophysical system parameters, which are hard to deduce from PIC simulations.