MODIFICATION OF LOW-FREQUENCY INSTABILITIES WITH HIGH-FREQUENCY PUMP WAVES

The influence of a large amplitude electric field oscillating near the upper hybrid frequency two (omega(0) similar to omega(uh)) on low-fre quency (LF) electrostatic flute type instabilities, where the pump fre quency (omega(0)/2 pi) is 2.45 GHz, is investigated in a pure toroidal plasma. Argon plasma is produced using a hot cathode discharge and mi crowaves are launched in the ordinary mode. Measurements reveal that t he amplitude of the dominant fluctuating component in the cross power spectrum of density and floating potential fluctuations is suppressed for omega(0) < omega(uh), whereas the amplitude of the fluctuations in creases in the case omega(0) > omega(uh).