Gyrokinetic Particle Simulation Of Nonlinear Evolution Of Mirror Instability
Authors: Peter Porazik and Jay R. Johnson
Abstract:
A gyrokinetic simulation model for nonlinear studies of the mirror instability
is described. The model is set in a uniform, periodic slab with anisotropic ions and
cold electrons. Particle-in-cell simulations with a noise reducing δf algorithm show agreement
with the linear theory of the mirror instability. Results of nonlinear simulations
near marginal stability are presented. Single-mode simulations show saturation due to
trapping. Simulations with a spectrum of unstable modes show that the negative magnetic
perturbations saturate at a lower amplitude and earlier than the positive magnetic
perturbations, which results in the development of peaked saturated structures. The saturation
amplitude of negative magnetic perturbations is in agreement with the trapped
particle theory, while the saturation amplitude of the positive magnetic perturbations
is determined by the local change in the Β⊥ (ratio of perpendicular plasma pressure to
magnetic pressure) parameter.
__________________________________________________
Submitted to: Journal of Geophysical Research (July 2013)
__________________________________________________
Download PPPL-4937 (pdf 958 KB 7 pp)
__________________________________________________