Two-dimensional eigenmode analysis of long-wavelength microinstabilities in rotating axisymmetric plasmas

The authors present a two-dimensional study of sheared flow effects on the kinetic trapped-ion and toroidal ion temperature gradient instabilities. The governing electrostatic gyrokinetic equation for rotating axisymmetric plasmas with Mach numbers of order unity is formulated. In the long-wavelength limit, (krρbi < 1), this equation is solved utilizing an improved version of the toroidal finite element code. Earlier local studies found that sheared toroidal flows will have a destabilizing effect on the trapped ion instability in both collisional and collisionless regimes. This effect is mainly due to the fact that the fraction of trapped particles is increased through electrostatic trapping. The ions are pushed outward due to centrifugal force and an electrostatic potential is set up by the electrons to achieve quasineutrality. The poloidal dependence of this potential in turn increases the number of trapped particles. In this work the authors present results of the two-dimensional eigenmode analysis and discuss the implications of sheared toroidal flows on long-wavelength drift-type micro-instabilities in tokamaks