EFFECT OF COULOMB COLLISIONS ON SPACE-TIME ECHO IN A PLASMA

The attenuation of space-time echo in a plasma due to collisional relaxation of VanKampen waves is investigated. The Fokker - Planck and Lennard - Bernstein operators and relaxation approximation are employed as the collision integral. It is shown that it is possible to determine either the dynamic friction and diffusion coefficients in velocity space involved in the Fokker - Planck operator or else the effective electron collision frequency appearing in the two other model collision intergrals. A comparison of the experimental echo characteristics with the predictions of the theory should permit one to assess the correctness of employing either of the model collision integrals for a real plasma.