Electron-positron cascade in magnetospheres of supermassive black holes

Supermassive black holes are known to produce powerful relativistic jets, such as in quasars and AGNs. These jets are thought to be powered by the Blandford-Znajek mechanism, which taps the spin energy of the BH into the electromagnetic Poynting flux. This mechanism requires the presence of plasma to carry current. Theoretical and numerical 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.