“…Both these scenarios are probably underestimating the magnetic energy in the cluster centre, because the finite Reynolds number achieved in our run (R e ≤ 500, based on R e ∼ 0.5 N 4/3 , where N is the 1-dimensional size of the high-resolution domain of the simulations, in number of cells, e.g., [48]) likely causes a delayed start of the small-scale dynamo amplification, compared to reality (e.g., [37]). Limited to the single case of the Coma cluster, our primordial seeding run seems to be in better agreement with the observational results of Faraday Rotation (e.g., [49,50]), which suggests a distribution of magnetic energy that scales with the gas thermal energy, and a significant magnetisation in the outskirts (even if limited to a single narrow sector of Coma, e.g., [50]); • The cosmic-ray energy goes from the upper limit obtained with out post-processing modelling of tracers [39] to zero in case no CR-protons are accelerated by shocks within the cluster. The increasing trend with radius of the CR-energy follows from the sharp increase of the acceleration efficiency as a function of Mach number, which rapidly increase towards cluster outskirts (e.g., [38]).…”