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Galactic magnetic fields seeded by ultralight dark photons

Joshua Berger1,*, Amit Bhoonah2,†, Joseph Bramante3,4,5,‡, J. Leo Kim6,3,4,§, Ningqiang Song7,∥, and Lawrence M. Widrow3,¶

  • *Contact author: joshua.berger@colostate.edu
  • †Contact author: amit.bhoonah@pitt.edu
  • ‡Contact author: joseph.bramante@queensu.ca
  • §Contact author: jlkim@yorku.ca
  • ∥Contact author: songnq@itp.ac.cn
  • Contact author: widrow@queensu.ca
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Phys. Rev. D 113, 043013 – Published 6 February, 2026

DOI: https://doi.org/10.1103/dbbc-pw52

Abstract

In this work, we show that ultralight dark photons, which couple to the Standard Model photon through kinetic mixing, can potentially source galactic scale magnetic fields. Although these magnetic fields would be too weak to detect at present in galaxies due to plasma screening effects, we show that dark photons can provide the seed magnetic field strength (10−20  G) required for dynamo amplification in galaxies. Such dynamo-amplified magnetic fields are consistent with observations of μG strength galactic magnetic fields.

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Phys. Rev. D 113, 043013– Published 6 February, 2026
  • Received 19 November 2025
  • Accepted 21 January 2026
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