  The excess in extreme-ultraviolet (EUV) radiation and high energy X-rays
(HEX) of Coma may be modeled by power law spectra. Their origin could be
inverse Compton (IC) emission by relativistic electrons. The scattered photon
fields can either be the CMB or the starlight of the galaxies within the
cluster. If the EUV excess is due to CMB-IC, a strongly inhomogeneous
magnetized intra- cluster medium (ICM) is required, in which the density of the
relativistic electrons is anticorrelated with the magnetic fields. This could
be understood if the electrons were accelerated during a major merger event
within the last 2 Gyr and cooled afterwards in the inhomogeneous fields. If the
EUV excess is due to starlight-IC, a population of relativistic, very low
energy electrons has to be present, with a high energy density. In order to
survive Coulomb losses, these electrons have to be separated from the cluster
gas by confining magnetic fields. This could be remnant radio plasma from the
epoch of violent quasar activity. The observed narrow radial profile of the EUV
excess emission is due to the narrow photon distribution for this model. Both
models favor very inhomogeneous magnetic field and relativistic electron
distributions. IC models for the HEX excess seem to be implausible: CMB-IC
leads to a mainly unmagnetized ICM, in contradiction to Faraday rotation
measurements. Starlight scattering electrons would overproduce EUV photons due
to simultaneously CMB-IC. We propose that the observed HEX excess is due to
bremsstrahlung of a small high energy power-law tail of the mainly thermal ICM
electron distribution. Such a tail is expected due to in-situ acceleration by
turbulence.
