Parametric Excitation of Plasma Waves by Gravitational Radiation

We consider the parametric excitation of a Langmuir wave and an electromagnetic wave by gravitational radiation, in a thin plasma on a Minkowski background. We calculate the coupling coefficients starting from a kinetic description. The growth rate of the instability is thus found. The Manley-Rowe relations are fulfilled only in the limit of a cold plasma. As a consequence, it is generally difficult to view the process quantum mechanically, i.e., as the decay of a graviton into a photon and a plasmon. Finally we discuss the relevance of our investigation to realistic physical situations and present an example.