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.

High frequency geodesic acoustic modes in electron scale turbulence

“…The diamagnetic frequency is ω ⋆ ∼ k θ ρ e c e /L n , k ⊥ and k are the perpendicular and the parallel wave numbers. The ETG model consists of a combination of ion and electron fluid dynamics coupled through quasineutrality, including finite β-effects [13,15].…”

“…(8), (9) and the non-adiabatic response Eq. (15) giving an approximation of the total stress of the form…”

“…The electron temperature gradient (ETG) mode driven by a combination of electron temperature gradients and field line curvature effects is a likely candidate for driving electron heat transport [10,11,12,13,14,15]. The ETG driven electron heat transport is determined by short scale fluctuations that do not influence ion heat transport and is largely unaffected by the large scale flows stabilizing ion-temperaturegradient (ITG) modes.…”

Computation of Growth Rates and Threshold of the Electromagnetic Electron Temperature Gradient Modes in Tokamaks

“…This fluid model is analogous to the fluid equations used in Refs. ( [9], [10], [11]). The governing model equations are electron continuity equation, parallel momentum-equation and temperature equation:…”

“…The main goal therefore, is to present application of differentiation matrices to linear analysis of ballooning modes. In the present paper, features of the collisionless, linear electromagnetic ETG mode [10,12] are investigated used as a specific expample of ballooning type modes. The ETG mode is widely recognized as a mechanism for the small scale turbulence driven electron heat transport in tokamaks.…”