WAVES IN AN INHOMOGENEOUS PLASMA IN AN ALTERNATING ELECTRIC FIELD.

Parametric wave excitation in an inhomogeneous plasma is investigated. The wave spectrum generally contains complex frequencies and is continuous and bounded. The existence of spectral boundary points leads to terms in the asymptotic expression for the potential for long time intervals which reflect oscillations at the boundary frequencies. In determining the frequency and growth rate of surface waves it is necessary to take into account the relative positions of the branches of the continuous spectrum on the complex frequency plane. The asymptotic expansion of the potential for long time intervals contains singular surface perturbations, which result from the branch points in the Laplace transform of the potential.