  The Buneman and ion acoustic instabilities are usually associated with
different electron and ion drift velocities, in such a way that there is a
large current through the plasma. However, due to the recently discovered
current-driven Langmuir oscillations (1-3), the relative drift velocity in
these configurations will oscillate at the plasma frequency, and with an
amplitude of at least the initial drift velocity. In contrast, the textbooks
assume a constant drift velocity. Since the growth rates arrived at under that
assumption are far less than the plasma frequency, several oscillation periods
will take place during the linear growth phase, and this will dampen the
instabilities. We provide general theoretical derivations of these
oscillations, and show simulation results of the altered behavior of the
instabilities. Towards the end, we hypothesize that drift-averaging might be a
viable method of calculating the modified growth rates.
