Radiation from Pulsed Electron Beams in Space Plasmas

摘要

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. This study was comprised of three parts. In the first part the number of beam pulses was assumed finite, and the beam was assumed to extend from z = minus infinity to plus infinity. In the second part we assumed as infinite pulse train and took into account that the beam extends only in the half-space from z=0 (the gun position) outward to infinity. Formulas for the radiation as a function of ray angle, propagation angle, electron beam pulse width and separation, and beam current, voltage and pitch angle were determined. Predictions of the power radiated were made for representative examples. In the third part the theory was generalized to the near field region. Keywords: Radiation; Pulsed Electron Beams; Space Plasmas; Coherent Spontaneous Emission; Cerenkov Radiation; Cyclotron Radiation.