  Collective properties of the quark-gluon medium induced by its polarization
are described by macroscopic QCD equations. The parton currents traversing it
lead to emission of Cherenkov gluons, the wake effect and the transition
radiation. Comparison with experimental data of RHIC reveals large value of the
chromopermittivity of the medium while cosmic ray data at higher energies
(close to LHC) favor much smaller values. The dispersion equations show that
the proper modes of the medium are unstable.
