A simple model of high harmonic generation in a plasma

We apply the average electron model to describe high harmonic generation in a collisional plasma in a laser field. The model is based on the coupled k inetic equations for electron velocity and electron temperature. The harmon ic intensities are obtained from the Fourier coefficients of the nonlinear part of the electron velocity. Numerical calculations are reported for both strongly and weakly ionized plasmas in the nonstationary regime. We shaw t he role of collisions frequencies as well as of quiver and thermal velociti es in the harmonic generation efficiency.