Nonstationarity of diffusion-controlled surface-wave-sustained discharges in a cw regime

The theory of the cw regime of maintenance of surface-wave-sustained gas discharges developed up to now is for discharge production at a given frequency. A generalization of this theory is presented here by considering discharge maintenance by a narrow-band signal, the actual situation in the experiments. Discharge production in a diffusion-controlled regime is treated within the fluid plasma theory. The set of the equations is for the interrelated variations along the discharge length of the time-dependent envelope of the electric field maintaining the plasma and for the time-dependent plasma characteristics (plasma density, electron temperature, power Θ absorbed on average by an electron). The numerical results presented for the time-space variations of wave-field amplitude and plasma density describe the nonstationary state of the cw regime of discharge maintenance. Detailed analysis with deterministic signals (Gaussian and super-Gaussian pulses) superimposed on a stationary cw-power level demonstrate different types of nonlinear effects--self-steepening and spontaneous modulation near the pulse edge--which are reminiscent of phenomena known from the nonlinear optics. The results for discharge maintenance by a high-frequency power modulated by a narrow-band low-amplitude Gaussian noise are discussed in terms of discharge stability/instability. Relevance to experimental finding in surface-wave-sustained discharge is commented on