Kinetic electron closures for electromagnetic simulation of drift and shear-Alfvén waves. II

Abstract

An electromagnetic hybrid scheme (fluid electrons and gyrokinetic ions) is elaborated in example calculations and extended to toroidal geometry. The scheme includes a kinetic electron closure valid for βe>me/mi (βe is the ratio of the plasma electron pressure to the magnetic field energy density). The new scheme incorporates partially linearized (δf ) drift-kinetic electrons whose pressure and number density moments are used to close the fluid momentum equation for the electron fluid (Ohm’s law). The test cases used are small-amplitude kinetic shear-Alfvén waves with electron Landau damping, the ion-temperature-gradient instability, and the collisionless drift instability (universal mode) in an unsheared slab as a function of the plasma βe. Attention is given to resolution and convergence issues in simulations of turbulent steady states.