Electron beam interactions with ions in a warm plasma

Conditions are determined for which the ions of a plasma might gain appreciable energy from the interaction with an electron beam. The waves along the magnetic field in a one-dimensional beam-plasma system are examined. For a cold plasma, the transverse waves exhibit a convective instability near the ion cyclotron frequency and a nonconvective instability at very low frequencies. The convective instability is greatly altered by a finite ion temperature, whereas the low frequency instability is relatively unaffected by temperature. For a weak beam, the longitudinal interaction occurs above the electron plasma frequency unless V/sub o/ < T/sub e/, where V/sub o/ is the d-c beam voltage and T/sub e/ is the electron temperature. A very strong interaction at the ion plasma frequency arises if (n/sub b//n) (T/sub e//V/sub o/)> 1, where n/sub b/ and n/sub p/ are the beam and plasma densities. For both transverse and longitudinal interactions it is shown that the presence of damping (cyclotron or Landau) can give rise to resistive medium type instabilities. Some brief results will also be given on the interactions in finite geometries which include the electron temperature. (auth)