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Examines the energy relations for surface waves. Use of auxiliary driving term in the determination of energy flow and stored energy for wave types; Mathematical representations of particle velocity; Transposition of tensors and vectors.

By inclusion of an external driving force, wave motion of any kind can be characterized by a dispersion function. This function is closely related to the energetic properties of wave motion, and then also to the averaged Lagrangian density. Linear and non-linear wave interaction can be analysed by inclusion of internal driving forces. Normalization procedures for the amplitudes can be avoided and time and space perturbations studied simultaneously. This analysis is further connected to slowly varying amplitudes and quasi-monochromatic waves. This paper presents the above-mentioned method and applies it to linear two-wave coupling, and non-linear three-wave coupling between positive and negative energy waves, and finally to amplitude modulation. The general equations obtained by this procedure are useful for general discussions. The simplicity of the method may prove useful in different applications.
The aim of this paper is to present a new and a simple method for analysis of wave interaction in dispersive media and to apply it on some illustrative problems. Further applications, which are found in plasma physics, microwave components and so on, will be presented later. [ABSTRACT FROM AUTHOR]

A plane wave is incident upon a bounded, cold plasma with a density varying periodically in time and space due to a high power pump wave. The modulation of the medium will produce a spectrum of reflected and transmitted components in different directions and with different frequencies. Inside the medium parametric effects will occur. The analysis takes into account all the time and space harmonics inside the medium and the reflection and transmission coefficients outside the medium. Four different types of wave interaction are obtained. Particularly the case of travelling-wave amplification is extensively studied by means of approximate analysis as well as computer analysis. It is found that when the width of the medium exceeds a critical value, a gain saturation is obtained and degenerate oscillations may occur. If the pump wave propagates obliquely, the maximum angular separation will be between the amplified components. [ABSTRACT FROM AUTHOR]