Characteristics and generation mechanism of holes in an extended electron vortex.

In nonneutral plasma, depleted regions (holes) in the vorticity often play a controlling role in the evolution of two-dimensional turbulence. We report experimental investigations of the generation process of ring holes (three-dimensionally annular depletion) surrounding a strongly-peaked clump of vorticity (point vortex) immersed in the background of a spatially extended vorticity distribution, and determine the empirical scaling for the generation time of the ring holes. Moreover, we report geometrical features of the ring hole, and report that ring holes play an important role for crystallization. [ABSTRACT FROM AUTHOR]