COLLISIONAL AMPLIFICATION OF TEST ELECTROMAGNETIC-WAVES IN A PLASMA SUBJECT TO AN INTENSE HIGH-FREQUENCY LASER FIELD

Recently, calculations based on Fokker-Planck and Landau collision ope rators have been used to demonstrate that test waves with electric fie lds in the plane of polarization of external superintense laser fields can get amplified by nonlinear collisional processes. The calculation s are similar in spirit to parametric instability calculations and mak e use of an averaging process for the collision operator whose range o f validity is not clear. The Dawson-Oberman model of high-frequency pl asma conductivity is used to reinvestigate this problem. It is shown t hat in the limit of small test wave frequency, omega(1) /omega(0) = ep silon much less than 1, no amplification is possible. This result cont radicts the one obtained by earlier workers with averaged collision op erators. At higher test wave frequencies earlier results are recovered . (C) 1998 American Institute of Physics. [S1070-664X(98)00507-2]