Radiation from pulsed electron beams in space plasmas

Abstract

A theoretical study has been made of the electromagnetic radiation arising from pulsed electron beams. The study assumes an electron beam which has a well‐organized spatial structure determined by a fixed trajectory in a magnetic field and on/off pulsing governed by the electron source. From this model the electromagnetic radiation is determined by adding coherently the radiation from each individual electron in the helical stream. The radiation per unit frequency interval is determined, as well as the radiation per unit solid angle, as a function of both propagation and ray angles, electron beam pulse width and separation, total number of pulses, and beam current. As expected for a coherent process, it is found that the radiated power varies at the square of the beam current. The relatively high efficiency of the beam in producing electromagnetic radiation is illustrated by consideration, among others, of a 1‐keV, 100‐mA beam used in recent experiments on the space shuttle. For these parameters the total radiated power per steradian is calculated at selected angles to be greater than 1% of the total beam power carried as electron kinetic energy. These results provide a useful theoretical basis for planning future electron beam experiments in space plasmas.

Whistler waves emission by a modulated electron beam: Nonlinear theory

“…Recent results on Cherenkov emission of whistlers produced during the interaction of a modulated electron beam with a magnetized plasma were also obtained in laboratory experiments. 8,9 In previous theoretical works, [10][11][12][13][14][15][16] the emission of electromagnetic waves in a magnetized plasma by a modulated electron beam has been considered in the assumption of given beam modulation ͑fixed beam͒; the evolution of the beam due to its interactions with the waves was not taken into account. In these studies attention was focused mainly on the determination of emission rates; calculations of electric and magnetic fields profiles were also presented.…”

Whistler waves produced by a modulated spiraling electron beam: Linear approach

“…Moreover, we suppose that the beam, injected at a finite pitch angle keeps its thickness unchanged, much less than the Larmor radius, forming a spiral structure. Such a structure was considered in many theoretical works [13][14][15][16] and observed in laboratory experiments, 9,18 as well as in space. It is clear that during the interaction of beam electrons with induced electromagnetic fields, this spiral structure will be spread.…”

“…In spite of the fact that the theory of whistler wave interaction with a modulated electron beam has been considered in many papers, [11][12][13][14][15][16][17] some problems remain unresolved. Indeed, the whistler features were not completely clarified and the fields characteristics were not considered in all the details, which are necessary for the study of nonlinear processes.…”

Whistler Wave Emission from a Modulated Electron Beam in a Collisional Magnetoplasma in the Presence of a Density Duct

“…Whistler wave excitation by pulsed or modulated charged-particle beams has been studied in many experimental [1][2][3][4][5][6][7] and theoretical [8][9][10][11][12][13][14][15][16] works. Interest in this field is in particular related to exploring possibilities of using such beams as sources of electromagnetic radiation in the near-Earth and laboratory plasmas (see, e.g., [13] and references therein).…”