Effects of impurity seeding and charge non-neutrality on electromagnetic electron temperature gradient modes in a tokamak

Abstract

A linear theory of toroidal electromagnetic electron temperature gradient (ETG) mode is reported. The effects such as Debye shielding, impurities, magnetic flutter perturbations δB_⊥ and compressible parallel magnetic field perturbations δB_|| are included in a fluid model. An eigenvalue equation is derived and solved analytically in local and semilocal limits. In the nonlocal limit, the eigenvalue equations are solved numerically. A comparison is also made of the linear thresholds obtained from this simple fluid model with previous gyrokinetic simulations. It is shown that the simple fluid theory results compare well with the thresholds obtained from gyrokinetic simulations.