Experimental, investigation of coherent parametric microwave absorption in magnetized inhomogeneous plasma

The generation of a coherent anti-stokes component of scattered microwave radiation is investigated experimentally in magnetized inhomogeneous plasma and shown to be related to the excitation of absolute stimulated forward scattering instability 1 --> 1' + s. The absolute parametric instability mechanism is related to the existence of two closely localized points in the plasma, where the three-wave decay conditions are fulfilled. The experimentally obtained values of thresholds, increments and frequency spectra of the instability are compared to theoretical predictions. The parametric interaction is shown to stay coherent well above the threshold, when it is responsible for the strong anomalous absorption of the microwave power.