# Electron-Positron Cascade in Magnetospheres of Spinning Black Holes

## TL;DR

This paper investigates the conditions under which electron-positron cascades in the magnetospheres of spinning black holes enable the Blandford-Znajek mechanism to extract rotational energy and power relativistic jets.

## Contribution

It provides a quantitative analysis of plasma generation conditions necessary for the Blandford-Znajek process in Kerr black hole magnetospheres.

## Key findings

- Identifies key plasma density thresholds for effective energy extraction.
- Analyzes the role of electron-positron cascades in jet formation.
- Highlights differences between black hole and neutron star magnetospheres.

## Abstract

We quantitatively study the stationary, axisymmetric, force-free magnetospheres of spinning (Kerr) black holes (BHs) and the conditions needed for relativistic jets to be powered by the Blandford-Znajek mechanism. These jets could be from active galactic nuclei, blazars, quasars, micro-quasars, radio active galaxies, and other systems that host Kerr BHs. The structure of the magnetosphere determines how the BH energy is extracted, e.g., via Blandford-Znajek mechanism, which converts the BH rotational energy into Poynting flux. The key assumption is the force-free condition, which requires the presence of plasma with the density being above the Goldreich-Julian density. Unlike neutron stars, which in principle can supply electrons from the surface, BH cannot supply plasma at all. The plasma must be generated \em{in situ} via an electron-positron cascade, presumably in the gap region. Here we study varying conditions that provide a sufficient amount of plasma for the Blandford-Znajek mechanism to work effectively.