On hydrodynamic description of waves in a relativistic plasma with allowance for deceleration by radiation

Linear oscillations of a relativistic plasma are investigated with an allowance for slowing-down by radiation in the hydrodynamic approximation. A relativistically invariant dispersion ralation is obtained and analyzed for an immovable plasma in the absence of external field, for plasma moving with a constant average velocity, and for waves propagating in directions parallel and perpendicular to an external magnetic field. It is shown that energy losses in collective radiation of electrons lead to damping of all types of plasma oscillations. This damping exceeds that of Landau for waves in a plasma of density n (>=) 109 cm3, whose velocity is at least one order higher than the thermal velocity of electrons