Excitation of ion-acoustic-like waves by subcritical currents in a plasma having equal electron and ion temperatures.

The effect of a magnetic-field-aligned plasma flow with a transverse velocity gradient on the excitation of current-driven ion-acoustic-like waves in a plasma having equal electron and ion temperatures (T(e) = T(i)) was investigated experimentally. In agreement with theoretical predictions, the presence of sheared plasma flow substantially reduces the critical electron drift velocity needed to produce the ion-acoustic instability.