Current-driven instabilities and resultant anomalous effects in isothermal, inhomogeneous plasmas

The evolution and effects of current-driven instabilities in isothermal, inhomogeneous plasmas are investigated in both theory and experiment. Sucessive destabilizations of four different instabilities, low-frequency drift wave, ion-cyclotron drift wave, high-frequency (continuous-spectrum ion-cyclotron) drift wave, and high-frequency electron wave, are observed in Q-device plasmas with increased current, and explained by a theory based on fluid and kinetic equations. Anomalous effects resulting from wave-particle interactions, i.e., enhanced resistivity, ion heating, and electron viscosity, are compared with predictions based on quasi-linear calculations. Analogous to ion sound causing important anomalies in the transport coefficients for plasmas with Te/Ti≫1, high-frequency, continuous-spectrum drift waves determine anomalous plasma behavior in inhomogeneous plasmas with Te/Ti≃1.