Configuration of Waves in Two-Plasmon Decay Instability Under Weak Landau Damping of Plasma Waves

A sufficiently intense electromagnetic wave, incident into a plasma, can decay into two electron plasma waves near quarter critical density layer of the plasma. This two-plasmon decay instability has been a hot topic mainly due to relevance to laser fusion in that the instability produces hot electrons causing a preheat problem. It has been known that configuration of wave vectors of the three waves involved in the instability is described by a hyperbola. However, recently there appeared a theoretical result that above a certain temperature (depending on density of the plasma) the configuration of waves should be described by a lemniscate rather than by a hyperbola.
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Thus the combined hyperbolalemniscate curve should be used in describing the configuration. Now we investigated effect of Landau damping of plasma waves on the instability. Thus near the transition temperature between hyperbola and lemniscate, a significant deviation from the hyperbola-lemniscate configuration was found theoretically. Temperature range of significant deviation from the hyperbola-lemniscate will be given and a numerical plot will be presented on overall behaviour of the configuration.