| Description: |
A nonlinear theory of the interaction of an external pump field with ion‐acoustic and h.f. surface waves in a plasma layer with inhomogeneous boundary regions is presented for the case, when the pump field frequency is less than the electron plasma frequency. The evolution of the parametrically excited turbulence and its stationary state are both analytically treated and numerically demonstrated. Dependent on the pump field strength, two mechanisms are to be distinguished: (i) nonlinear generation of damped ion‐acoustic harmonics, (ii) cascade excitation of secondary eigenmodes by growing surface oscillations. At only slight overthreshold values, mechanism (i) is responsible for the occurence of the steady state, whereas, for higher pump field strength, the wave amplitudes as well as their saturated levels are mainly determined by mechanism (ii). |