Electromagnetic wave radiation by an electron beam spiraling in a magnetized plasma column

Abstract

The paper studies the electromagnetic wave radiation by a density modulated and thin electron beam of finite length injected obliquely with respect to the constant external magnetic field into a cylindrical plasma column embedded in a homogeneous medium (plasma, dielectric, or free space) and aligned along the magnetic field lines. The time-averaged power radiated at the modulation frequency is determined as a function of the beam, the plasma column, and the medium parameters. Particular attention is devoted to the case when the beam modulation frequency belongs to the whistler frequency band. The paper shows what significant differences exist between the physical features of the emissions when the beam radiates in a plasma column embedded in a homogeneous medium or in a uniform and unbounded magnetized plasma. Based on the results of numerical calculations, the time-averaged power radiated by pulsed and modulated beams has been estimated for typical laboratory plasma experiments. In particular, it is shown that a beam propagating in a plasma column can efficiently enhance its wave emission due to Cherenkov and normal cyclotron excitation of guided whistler modes.