A KINETIC DESCRIPTION OF ELECTRON-BEAM EJECTION FROM SPACECRAFT

A model based on the Boltzmann kinetic equation describing electron be am ejection from spacecraft is presented. Results are shown for steady -state, beam-atmosphere interaction (BAI) and for beam-plasma interact ion (BPI). The BPI considered is that of elastic scattering of beam el ectrons with strong, short-scale Langmuir turbulence. This mechanism h as been suggested for prompt echoes of beam electrons observed in soun ding rocket experiments. It is shown that the interaction is sufficien tly strong to account for observations of back-scattered electrons at the beam accelerator energy. However, it is clear from observations th at particles undergo diffusion in energy at a rate exeeding levels exp ected for BAI. Inelastic scattering in BPI must therefore also be impo rtant.