Tripolar vortex in a plasma

A tripolar vortex is spontaneously generated in a magnetized plasma. The flow velocity field of ions has been measured with a directional Langmuir probe, exhibiting the tripolar structure in vorticity distribution. The most remarkable feature of the tripolar vortex is that the polarity of rotation of each vortex is opposite to that of E /spl times/ B drift. It is found that the charge-exchange process with inhomogeneous background neutrals produces an effective force, which dominates the electric field and drives the plasma into anti-E /spl times/ B rotation.