Magnetic fields and cosmic rays in M 31 - I. Spectral indices, scale lengths, Faraday rotation, and magnetic field patternR. Beck, E. M. Berkhuijsen, R. Gießübel and D. D. MulcahyA&A, 633 (2020) A5DOI: https://doi.org/10.1051/0004-6361/201936481
