# A Cosmic Battery in accretion flows around astrophysical black holes

## TL;DR

This paper proposes a Cosmic Battery mechanism that explains how magnetic fields are generated and amplified in accretion flows around black holes, with implications for jet formation and magnetic field evolution.

## Contribution

It introduces a novel Cosmic Battery process driven by radiation-induced electric fields, demonstrating magnetic field growth to equipartition in black hole environments.

## Key findings

- Magnetic fields grow to equipartition over hundreds of millions of dynamical times.
- The process operates on timescales of weeks for stellar black holes and millions of years for supermassive black holes.
- Numerical and observational evidence supports the Cosmic Battery mechanism.

## Abstract

We present our view of the immediate environment of an astrophysical black hole. We discuss the origin of the electron-positron and electron-proton jet components, and the origin of the large-scale magnetic field. We show how the aberrated radiation field viewed by the rotating plasma generates an azimuthal induction electric field, and how the curl of this electric field steadily grows the magnetic field to equipartition over a few hundred million dynamical times. That timescale corresponds to weeks for stellar mass black holes, and million years for super-massive black holes. We conclude with numerical and observational confirmation of the action of a Cosmic Battery in accretion flows around astrophysical black holes.