| Issue |
A&A
Volume 709, May 2026
|
|
|---|---|---|
| Article Number | A45 | |
| Number of page(s) | 4 | |
| Section | Cosmology (including clusters of galaxies) | |
| DOI | https://doi.org/10.1051/0004-6361/202558395 | |
| Published online | 01 May 2026 | |
The contribution of galaxies to the magnetic field in cosmic voids
II. Institut für Theoretische Physik, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
★ Corresponding authors: This email address is being protected from spambots. You need JavaScript enabled to view it.
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Received:
4
December
2025
Accepted:
22
March
2026
Abstract
Context. Astrophysical processes can contribute to magnetic fields within cosmic voids either through magnetized outflows from the astrophysical large-scale structure or through the superposition of dipolar contributions from individual galaxies. Such astrophysical magnetic fields represent a foreground to possible space-filling primordial magnetic fields seeded in the early Universe.
Aims. In this paper, we provide a qualitative description of the diffusion of magnetic fields by intergalactic plasmas.
Methods. Using nonrelativistic magnetohydrodynamics, we derived general, analytic formulae for the magnetic field strength subject to diffusion in the presence of intergalactic plasma.
Results. We find that contributions from the superposition of static dipoles are highly suppressed and cannot explain indications for the lower bounds based on observations of γ-ray cascades from high-energy sources such as blazars.
Key words: magnetohydrodynamics (MHD) / plasmas / galaxies: magnetic fields
© The Authors 2026
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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