Plasma and Fusion Research
Online ISSN : 1880-6821
ISSN-L : 1880-6821
Letters
Role of Stable Modes in the ITG-Driven Instability in a Mode-Coupled System
Paul P. HILSCHERKenji IMADERAJiquan LIYasuaki KISHIMOTO
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2013 Volume 8 Pages 1303151

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Abstract

Kinetic damping in linear gyrokinetic (GK) Vlasov simulations is found to exhibit a bifurcation at the collisionality βc = β*c , above which, i.e. βc >β*c , the damping is represented by a Landau eigenmode in velocity space, while below which, i.e. βc < β*c , by the phase mixing of a finite number of marginally stable, discretized Case-van Kampen eigenmodes. The latter causes a recurrence that restricts the damping and then the energy transfer from wave to particles within a finite recurrence time. In order to address whether the stabilization effect due to such stable damped modes on unstable modes via mode coupling can be evaluated in long timescale GK simulations, we introduced a triad model consisting of stable and unstable modes incorporated with a tertiary vortex flow. We identified β*c numerically and found that the stabilization effect works properly beyond the recurrence time even in the phase mixing regime across βc = β*c .

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© 2013 by The Japan Society of Plasma Science and Nuclear Fusion Research
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