  A new technique for manipulation and control of gradient-driven instabilities
through nonlinear interaction with Alfv\'en waves in a laboratory plasma is
presented. A narrow field-aligned density depletion is created in the Large
Plasma Device (LAPD), resulting in coherent unstable fluctuations on the
periphery of the depletion. Two independent kinetic Alfv\'en waves are launched
along the depletion at separate frequencies, creating a nonlinear beat-wave
response at or near the frequency of the original instability. When the
beat-wave has sufficient amplitude, the original unstable mode is suppressed,
leaving only the beat-wave response at a different frequency, generally at
lower amplitude.
