1995A&A...302..680F

The polarization data of the radio galaxy NGC 4869, belonging to the Coma cluster and located in its central region, allow us to obtain information on the structure of magnetic field associated with the cluster itself. A magnetic field of ≲8.3h^1/2₁₀₀µG, tangled on scales of the order of less than 1kpc, is required to explain the observed fluctuations of the rotation measure. This magnetic field is more than one order of magnitude stronger than the equipartition value obtained for Coma C. This implies that the halo source Coma C may not be at the equipartition. Moreover, the need of efficient reacceleration mechanisms for the electrons radiating in Coma C is stronger. The energy supply to the Coma C radiating electrons is probably provided by the cluster merger process.