Parametric excitation of electromagnetic radiation by intense Langmuir waves

Summary form only given. The authors consider various nonlinear mode-mode coupling processes involving the interaction of high-frequency Langmuir waves with low-frequency ion-acoustic waves or Alfven waves, which may excite electromagnetic waves near the plasma frequency. They discuss the parametric generation of electromagnetic waves in an unmagnetized plasma through the ponderomotive coupling of Langmuir and ion-acoustic waves. Based on the generalized Zakharov equations, they analyze the electromagnetic oscillating two-stream instability driven by a standing Langmuir pump. Depending on two detuning parameters, this instability can be either purely growing or convective, either up-conversion or down-conversion. They discuss the parametric excitation of electromagnetic waves in a magnetized plasma via the ponderomotive coupling of Langmuir and Alfven waves.