Backscattering decay processes in electron beam--plasma interactions including ion dynamics

Electron plasma waves driven unstable by the electron beam-plasma instability are observed to decay into convectively and absolutely growing ion waves and electron waves propagating in opposite directions. Ion waves excited to large amplitudes further couple with the high-frequency unstable waves to produce nonresonant short-wavelength electron modes. The nonresonant modes are found effective in accelerating electrons and thermalizing the beam.