Theory of Generation of Anomalous Scattering Spectra in Not-Dense Plasma under Conditions of Electron Cyclotron Microwave Heating at the Second Resonance Harmonic

The mechanisms are discussed for generation of frequency spectra of anomalous scattering in not-dense plasma during microwave heating using the extraordinary wave at the second resonance harmonic. The developed theory is used to interpret the results of experiments on electron cyclotron resonance heating (ECHR) of plasma in the Wendelstein 7-X stellarator, in which both the Stokes and anti-Stokes frequency bands were observed, shifted up and down with respect to the microwave frequency. The explanation is given for the paradoxical excess of the amplitude of the anti-Stokes spectral component over the Stokes component amplitude, which was observed in a number of experiments.