# Numerical simulations of the Cosmic Battery in accretion flows around astrophysical black holes

## TL;DR

This study uses advanced simulations to demonstrate the Cosmic Battery effect in black hole accretion flows, showing how radiation-induced electromagnetic forces can lead to magnetically arrested states with jet formation.

## Contribution

First simulation-based evidence showing the Cosmic Battery's role in generating large-scale magnetic fields in black hole accretion flows.

## Key findings

- Radiation pressure term leads to magnetically arrested state (MAD).
- Without the radiation term, the flow remains a standard accretion flow.
- Simulation confirms the secular action of the Cosmic Battery in astrophysical black holes.

## Abstract

We implement the KORAL code to perform two sets of very long general relativistic radiation magnetohydrodynamic simulations of an axisymmetric optically thin magnetized flow around a non-rotating black hole: one with a new term in the electromagnetic field tensor due to the radiation pressure felt by the plasma electrons on the comoving frame of the electron-proton plasma, and one without. The source of the radiation is the accretion flow itself. Without the new term, the system evolves to a standard accretion flow due to the development of the magneto-rotational instability (MRI). With the new term, however, the system eventually evolves to a magnetically arrested state (MAD) in which a large scale jet-like magnetic field threads the black hole horizon. Our results confirm the secular action of the Cosmic Battery in accretion flows around astrophysical black holes.