Sheared-flow-driven ion-acoustic drift-wave instability and the formation of quadrupolar vortices in a nonuniform electron-positron-ion magnetoplasma

A system of nonlinear equations which governs the dynamics of low-frequency (in comparison with the ion gyrofrequency) electrostatic waves in a nonuniform electron-positron-ion (e-p-i) magnetoplasma with sheared ion flows is presented. In the linear limit, a dispersion relation is obtained that admits new instabilities of drift-waves. It is found that ion-acoustic and electrostatic drift waves can become unstable due to ion sheared flow. Furthermore, the nonlinear interactions between these finite amplitude short-wavelength waves give rise to quadrupolar vortices. The relevance of the investigation to laboratory and astrophysical plasmas is pointed out. (C) 2004 American Institute of Physics.