Nonlinear electron beam interaction with a whistler wave packet

Abstract

The nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet through Cherenkov resonance is considered. It is shown that effective dissipation due to whistlers’ wave field leakage out of the bounded beam volume to infinity (effective radiation outside the beam) strongly influences the evolution of the beam electrons’ distribution. Self-organization of beam structure leads to the formation of electron bunches continuously decelerated by waves. In the presence of effective energy losses, the phases of all waves in the packet can become strongly correlated and thus can prevent the stochastic phase mixing required for validity of quasilinear theory. In the asymptotic stage of the beam–waves interaction, dynamically stable electron bunches are present together with a diffusion plateau in the velocity distribution; these nonlinear structures allow the beam to radiate wave energy on a significative distance from its injection point.