Radiation-induced solitary waves in hot plasmas
  It is argued that, in a hot plasma interacting with thermal radiation, there exist the radiation-induced solitary waves different from the types of nonlinear waves in plasmas known so far. There are extensive observational evidence for the propagation of these specific density waves in the hot plasmas of various astrophysical objects. Radiation produces also non-adiabatic density perturbations analogues to the second sound in the liquid helium. 
F.V.Prigara