ROTATION AND OSCILLATION OF NONLINEAR DIPOLE VORTEX IN THE DRIFT-UNSTABLE PLASMA

The behaviors of the nonlinear dipole vortex in the drift unstable pla sma are studied by numerical approaches. Model equations used in numer ical simulation are derived from two-fluid model and are composed of t wo equations with respect to the electrostatic potential and the densi ty perturbation. When the initial dipole vortex is inclined at some an gle with respect to the direction of the drift. velocity, the dipole v ortex oscillates or rotates in the first stage. These phenomenon also happen in the stable system. In the second stage, one part of the dipo le vortex grows and another decays because of the destabilization. The shrunk vortex rotates around the enlarged vortex. Consequently, a mon opole vortex appears out of the dipole vortex.