Effects of ExB velocity shear on electrostatic structures

Bursts of electrostatic turbulence measured in the edge region of two reversed field pinch experiments (RFX and T2R) are observed to be associated with electrostatic structures. The corresponding ExB velocity drifts have been reconstructed showing features reminiscent of monopolar vortices. These vortices have been grouped in two classes depending on their rotation direction. It is observed that the prevalent rotation direction depends on the shear of the surrounding mean ExB drift velocity, showing a clear analogy with ordinary fluids. (C) 2002 American Institute of Physics.