THEORY OF GENERATION OF ELECTRON-CYCLOTRON FREQUENCY HALF-INTEGER HARMONICS

A mechanism is considered for the generation of electrostatic waves with frequencies omega = (n + 1/2)omega(c) (where omega(c) is the electron-cyclotron frequency; n = 1, 2,...), which are observed in various space and laboratory plasmas. It is shown that the excitation of these waves can be explained by the interaction of Bernstein modes with electron beams or plasmas with shifted-Maxwellian distribution functions. The spectra of the corresponding instability are studied both analytically and numerically, It is shown that the waves with frequencies (n + 1/2)omega(c) stand out from those of the Bernstein-mode continuous spectrum because of their dispersion properties and are hardly due to any specific form of the interacting beam distribution function.