Experimental Evidence for Mode Selection in Turbulent Plasma Transport

A conditional sampling technique is used for analysing low-frequency electrostatic fluctuations in a strongly magnetized plasma. It is demonstrated that a large burstlike flux of plasma across magnetic-field lines is associated with the presence of pairs of large B-field aligned vortices having opposite polarity. Significant density fluctuations are simultaneously present but taken alone they contribute only little to the turbulent plasma flux. By their speed and direction of propagation the density fluctuations are identified as drift waves. The flute-type modes moving close to the ion drift velocity are mediating most of the enhanced plasma flux.