Collisional amplification of test electromagnetic waves in a plasma subject to an intense high-frequency laser field

Abstract

Recently, calculations based on Fokker-Planck and Landau collision operators have been used to demonstrate that test waves with electric fields in the plane of polarization of external superintense laser fields can get amplified by nonlinear collisional processes. The calculations are similar in spirit to parametric instability calculations and make use of an averaging process for the collision operator whose range of validity is not clear. The Dawson-Oberman model of high-frequency plasma conductivity is used to reinvestigate this problem. It is shown that in the limit of small test wave frequency, ω₁/ω₀ = ε«1, no amplification is possible. This result contradicts the one obtained by earlier workers with averaged collision operators. At higher test wave frequencies earlier results are recovered.