So far, a large number of analytical (quasilinear/weak turbulence), simulational (PIC/Vlasov), experimental, and observational studies have investigated various aspects of this problem such as the effect of weak/strong equilibrium magnetic field, relativistic/warm/cold beam, and background nonuniform/modulated density.
Solar type II and type III radio bursts are also attributed to the electron beam-plasma instabilities. There are some other studies that discussed other aspects of the beam-plasma interaction such as beam heating and characteristics of Langmuir electric field waveforms. The results of the Geotail waveform observation on the electrostatic plasma waves with their frequency close to the local electron plasma frequency in the tail lobe were presented by Kojima et al. suggested an interpretation of these spectra as signatures of nonlinear decay of Langmuir waves to electron-sound and ion-sound secondary waves. The intense high-frequency electrostatic waves observed in the terrestrial foreshock often have a form of a superposition of two monochromatic waves close to the plasma frequency. analyzed the complete spectrum of waves (0–4 MHz) and electron distributions during events of modulated Langmuir waves observed by Freja in the topside polar ionosphere. reported the observations of highly structured bursts of Langmuir waves produced by energetic electrons ejected from a solar flare using wideband plasma wave measurements on the Galileo spacecraft. Such an interaction is found to generate electromagnetic waves observed in space plasmas. IntroductionĮlectron beam-plasma interaction is a fundamental nonlinear plasma process that is frequently taking place in space environments and laboratory plasmas. Moreover, the dispersion diagrams of all excited waves are presented. This confirms the two-step wave-wave coupling mechanism for the generation of second harmonic electromagnetic waves, which requires the excitation of ion-acoustic waves in the first step. In the first two cases, m i/ m e = 0 and 1, there is no sign of emission in the second harmonic, while the strongest emission in the second harmonic is found for the case of largest mass ratio, m i/ m e = 1000. However, it determines the decay process of solitons and the excitation of electromagnetic waves in the second harmonic. It is shown that the generation of Langmuir waves in the fundamental mode of electron plasma frequency and the subsequent dynamics of large-amplitude solitons are not affected by the ion species. Four cases are considered: A: m i/ m e = 0 (two-electron stream instability) B: m i/ m e = 1 (pair plasma) C: m i/ m e = 100 and D: m i/ m e = 1000. Two-dimensional electromagnetic particle-in-cell simulations are carried out to investigate the effect of ion-to-electron mass ratio on the evolution of warm electron beam-plasma instability.