  With tantalizing evidence of the recent e-Rosita mission, re-discovering very
soft X-rays and EUV radiation from a cluster of galaxies or its environment,
the question of the origin of cluster EUV excess is revisited in this work. It
will be shown that the gas temperature, density, and frozen-in magnetic field
of the intracluster medium, collectively support the emission and propagation
of coherent \u{C}erenkov radiation, which is low frequency and large amplitude
radiation capable of accelerating charged particles to relativistic speeds.
Owing to the spectrum of \u{C}erenkov radiation, most of the incipient
relativistic electrons undergo inverse-Compton scattering with the cosmic
microwave background. It turns out the scattered radiation has observable
ramifications only in the EUV band, of photon energy $70 -- 100$~eV, having a
luminosity $\approx 10^{44}$~ergs~s$^{-1}$. This luminosity is on par with the
EUV excess level detected from Abell 1795 and the Coma cluster. It should be
stressed, as {\it caveat emptor}, that although the main subject is the
putative large amplitude coherent \u{C}erenkov modes which are highly
nonlinear, the results presented were derived using a quasi-linear approach to
highlight the observable features of the phenomenon, namely the EUV emission.
