Cyclotron amplification of whistler waves by nonstationary electron beams in an inhomogeneous magnetic field

Publisher Website
Google Scholar
Abstract
The linear amplification of whistler waves with varying frequency by beams of energetic electrons in the inhomogeneous magnetic field is studied. Rigorous treatment developed by Trakhtengerts et al. [Phys. Plasmas 6, 692 (1999)] for the distribution function with a steplike deformation over parallel velocities is applied here for the δ-like distribution which is appropriate for triggered emissions. The formalism developed enables one to determine the one-hop amplification of a wavelet with variable frequency and the “optimal” spatio-temporal variation of the frequency corresponding to the maximum amplification; we show this variation to coincide with the so-called second-order cyclotron resonance condition, similarly to the case of the steplike distribution. The results allow one to compare the dependence of the maximum amplification on characteristic parameters of a plasma in the magnetic trap for smooth, steplike, and beamlike distributions.