Magnetic fields in galactic haloes

TL;DR

This paper reviews the current understanding of magnetic fields in galactic haloes, highlighting observational challenges, configurations, and their interactions with other interstellar medium components.

Contribution

It synthesizes observational data and theoretical insights on galactic halo magnetic fields, emphasizing their complex structures and interactions.

Findings

Magnetic fields influence galactic ecosystems significantly.

Observational data on halo magnetic fields are limited and inconclusive.

Magnetic fields interact strongly with gas and cosmic rays.

Abstract

Magnetic fields on a range of scales play a large role in the ecosystems of galaxies, both in the galactic disk and in the extended layers of gas away from the plane. Observing magnetic field strength, structure and orientation is complex, and necessarily indirect. Observational data of magnetic fields in the halo of the Milky Way are scarce, and non-conclusive about the large-scale structure of the field. In external galaxies, various large-scale configurations of magnetic fields are measured, but many uncertainties about exact configurations and their origin remain. There is a strong interaction between magnetic fields and other components in the interstellar medium such as ionized and neutral gas and cosmic rays. The energy densities of these components are comparable on large scales, indicating that magnetic fields are not passive tracers but that magnetic field feedback on the other interstellar medium components needs to be taken into account.