Modifying interchange turbulence by application of rotating perturbations to a dipole-confined plasma

Measurements using the Collisionless Terella Experiment (CTX) determined the structure of turbulent and unstable interchange mixing. An ERCH generated plasma, in the low density regime the Hot Election Interchange instability dominates, while through the application of axisymmetric biasing at the inner boundary Centrifugal Interchange modes can be excited. With additional gas fueling the plasma undergoes a dramatic transition to a turbulent state. Statistical analysis of global and local measurements of the plasma fluctuations show plasma dynamics to be consistent with predictions of two-dimensional turbulence and with the presence of the nonlinear inverse-energy cascade to larger spatial scale. We report new experiments to directly modify the turbulent spectrum by amplifying or controlling individual wavelengths through the application of electrostatic perturbations. Rotating perturbations with both feedback phase-controlled and with constant frequency open-loop perturbations will be discussed.