Cosmic-ray driven dynamo in the medium of irregular galaxy

TL;DR

This paper models the cosmic-ray driven dynamo in irregular galaxies, demonstrating magnetic field amplification despite slow rotation and low shear, and highlighting the potential for intergalactic magnetic field seeding.

Contribution

It presents a numerical magnetohydrodynamical model showing magnetic field amplification in irregular galaxies with slow rotation, a scenario previously considered unfavorable.

Findings

Magnetic fields are amplified even with slow galactic rotation.

Significant magnetic energy flows out, contributing to intergalactic magnetic fields.

The model aligns with observations of magnetic fields in irregular galaxies.

Abstract

We investigate the cosmic ray driven dynamo in the interstellar medium of irregular galaxy. The observations (Chyzy et al. 2000, 2003) show that the magnetic field in irregular galaxies is present and its value reaches the same level as in spiral galaxies. However the conditions in the medium of irregular galaxy are very unfavorable for amplification the magnetic field due to slow rotation and low shearing rate. In this work we present numerical model of the interstellar medium in irregular galaxies. The model includes magnetohydrodynamical dynamo driven by cosmic rays in the interstellar medium provided by random supernova explosions. We describe models characterized by different shear and rotation. We find that even slow galactic rotation with low shearing rate gives amplification of the magnetic field. Simulations have shown that high amount of the magnetic energy flow out off the simulation region becoming an efficient source of intergalactic magnetic fields.