Parametric decays of a circularly polarized electromagnetic wave in an electron-positron magnetized plasma

Abstract

We study the parametric decays of an electromagnetic wave propagating along an external magnetic field in an electron-positron plasma. We include weakly relativistic effects on the particle motions in the wave field and the nonlinear ponderomotive force. We show that there are a number of resonant and nonresonant wave couplings. These include ordinary decay instabilities, in which the pump wave decays into an electroacoustic mode and a sideband wave. There are also nonresonant couplings involving two sideband waves and a nonresonant modulational instability in which the pump wave decays into two sideband modes. Depending on the parameters involved, there is a resonant modulational instability involving a forward-propagating electroacoustic mode and a sideband daughter wave.