Journal of Plasma Physics



Whistler emission through transition radiation by a modulated electron beam spiralling in a magnetoplasma


M. STARODUBTSEV a1 and C. KRAFFT a2
a1 Institute of Applied Physics, Russian Academy of Sciences, 603600 Nizhny-Novgorod, Russia
a2 Laboratoire de Physique des Gaz et des Plasmas, Université Paris Sud, 91405 Orsay Cedex, France

Abstract

Transition radiation from the zone of injection of a modulated electron beam spiralling into a magnetoplasma has been identified as whistler waves propagating quasiparallel to the external magnetic field. The characteristics of the radiation are similar to the emission by localized sources, such as loop antennas and electric dipoles: resonance-cone structures at low plasma densities and energy flow along the external magnetic field at higher densities, with a diverging radiation pattern and with whistler phase velocities inversely proportional to the plasma frequency. These studies should contribute to a wider understanding of the physical processes connected with the injection of charges in a magnetoplasma – either from a gun on board a spacecraft or in a plasma chamber – and thus allow the determination of appropriate radiator characteristics in order to control, to some extent, plasma perturbations and wave emission in the region of the injector.

(Received July 1 1999)