Oscillations Present in Plasma-Electron Heating by an Electron Beam

Oscillations of electrostatic fields present when electrons are strongly heated by electron-beam plasma interaction reveal large-amplitude oscillations with $\frac{\ensuremath{\omega}}{{k}_{\ensuremath{\parallel}}}\ensuremath{\lesssim}{v}_{b}$, the electron-beam speed; $\ensuremath{\omega}\ensuremath{\approx}\frac{{\ensuremath{\omega}}_{\mathrm{ce}}}{10}$, where ${\ensuremath{\omega}}_{\mathrm{ce}}$ is the electron gyrofrequency; coherence lengths of roughly a few wavelengths (<< plasma length); and maximum electrostatic potential in the wave approaching the applied beam voltage. A gross compatibility is found between the observed frequencies and wavelengths and the predictions of a linear theory.