Drift-wave instability excited by field-aligned ion flow velocity shear in the absence of electron current

The excitation of the drift-wave instability by the ion flow velocity shear in the absence of the electron drift flow was experimentally demonstrated. The fluctuation amplitude was observed to increase with increasing the shear strength, but the instability was found to be gradually stabilized when the shear strength exceeds the critical value. The experimental results are in good agreement with the dependence of the theoretical growth rate on the shear parameter, which is calculated in the kinetic treatment including the effect of the radial density gradient.