ON THE APPLICABILITY OF THE FLUID APPROACH TO THE DESCRIPTION OF BILINEAR INTERACTION AND SCATTERING OF WAVES IN PLASMAS

The cold fluid (CF) and the more general low-temperature kinetic (LTK) models of bilinear wave interaction and collective Thomson scattering have been the subject of exhaustive investigations. These have reveal ed that the CF model is inappropriate for its intended use: the modell ing of scattering from thermal fluctuations in the limit where the pla sma may be treated as cold for the incident and scattered waves, but n or cold for the fluctuations. Assuming the plasma to be cold for the f luctuations would be inconsistent with their thermal nature. In respon se it has been argued that the CF model is in accord with the LTK mode l when scattering is from cold collective oscillations. This is true, but irrelevant.