Shear flow effect on ion temperature gradient vortices in plasmas with sheared magnetic field

Abstract

The effect of velocity shear on ion temperature gradient (ITG) driven vortices in a nonuniform plasma in a curved, sheared magnetic field is investigated. In absence of parallel ion dynamics, vortex solutions for the ITG mode are studied analytically. It is shown that under certain conditions the coupled equations for potential and pressure exhibit special tripolar vortex-like structures. For the general case, however, parallel ion dynamics is included and the equation describing the stationary ITG vortex has the structure of a nonlinear Poisson-type equation. Analytical as well as numerical solutions of this equation are presented for various possible cases. It is shown that, for a critical value of the velocity shear asymmetric dipolar vortices can arise which are strongly modified as a localized vortex chain at resonance. For strong velocity shear these structures are destroyed and ultimately lead to a dominating monopolar form. The effects of magnetic shear indicate it may destroy these structures.