Dynamics of electron-plasma vortex in background vorticity distribution

Dynamics of a point vortex in interaction with a broad profile of backgroun d vorticity is studied experimentally by using an electron plasma. The obse rved motion of the vortex compares favorably with a recently proposed theor etical model [D.A. Schecter and D.H.E. Dubin, Phys. Rev. Lett. 83, 2191 (19 99)]. Perturbations in the background distribution in the wake of the spira l orbit of the vortex amount to several tens of percent and are considered to be a major reason for deviations of the observation from the linear theo retical model.