Conditional eddies, or clumps, in ion-beam-generated turbulence

Low-frequency electrostatic fluctuations are investigated experimentally in an unmagnetized plasma. The turbulence is generated by ion-ion-beam instabilities. Real-time signals are recorded and investigated statistically on a conditional basis. The formation and propagation of structures with a relatively long lifetime in terms of the average bounce period is observed.

Particles bouncing in the potential well associated with these `eddies' will necessarily remain correlated for times determined by the eddy lifetime. The results thus provide evidence for clump formation in plasmas