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arXiv · 1812.08566

The effect of background flow shear on gyrokinetic turbulence in the cold ion limit

Justin Ball·Stephan Brunner·Ben F. McMillan
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Abstract

The cold ion limit of the local gyrokinetic model is rigorously taken to produce a nonlinear system of fluid equations that includes background flow shear. No fluid closure is required. By considering a simple slab geometry with magnetic drifts, but no magnetic shear, these fluid equations reduce to the Charney-Hasegawa-Mima model in the presence of flow shear. Analytic solutions to this model are found to study the impact of ExB flow shear on the stability of a single Parallel Velocity Gradient (PVG) driven mode. Additionally, the model is used to investigate the effect of background ExB flow shear on the basic three-mode nonlinear coupling, which reveals differences between zonal and non-zonal modes. These analytic results agree with gyrokinetic simulations and can serve to benchmark the numerical implementation of flow shear and nonlinear coupling.

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Justin Ball, Stephan Brunner, Ben F. McMillan. 2018-12-20. The effect of background flow shear on gyrokinetic turbulence in the cold ion limit. https://doi.org/10.1088/1361-6587%2Fab1320

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