Electron temperature gradient instability in toroidal plasmas

Electron temperature gradient (ETG) driven instability in toroidal plasmas is studied with gyrokinetic theory. The full electron kinetics including finite Larmor radius effects, toroidal (curvature and magnetic gradient) drift motion ωD, and transit k∥v∥, is considered. The upgraded numerical scheme for solving the integral eigenvalue equations allows the study of both growing and damping modes, and thus direct calculation of critical gradient. A systematic parameter study is carried out for low β(=plasma pressure/magnetic pressure) circular flux surface equilibria. The basic characteristics of the modes are discussed. The scaling of the critical gradient with respect to toroidicity and to the ratio of electron temperature over ion temperature is obtained. Estimation for the transport induced by the modes is given.