Features of the Spectrum of Non-Thermal Cyclotron Emission of an Electron Cyclotron Resonance Discharge Plasma in an Open Magnetic Trap

We discuss features of the fine structure of the cyclotron radiation spectrum produced by the plasma of an electron cyclotron resonance (ECR) discharge in a wide range of experimental parameters. In a nonequilibrium plasma, a cyclotron instability develops, which leads to the generation of electromagnetic emission bursts in the whistler frequency range. Simultaneously with the generation of whistler waves, low-frequency oscillations were discovered for the first time, which modify the spectrum of high-frequency waves. It is shown that in the presence of low-frequency oscillations, the frequency and amplitude of high-frequency whistler waves are modulated at the frequency of the low-frequency wave. The formation of a broadband spectrum of whistlers with many sidebands in the Fourier spectrum is determined by the nonlinear interaction of high-frequency electromagnetic oscillations with low-frequency plasma waves in the lower hybrid frequency range.