[Table of Contents]

Plasma and Fusion Research

Volume 8, 1303151 (2013)

Letters

Role of Stable Modes in the ITG-Driven Instability in a Mode-Coupled System
Paul P. HILSCHER1), Kenji IMADERA1), Jiquan LI1) and Yasuaki KISHIMOTO1,2)
1)
Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
2)
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
(Received 10 June 2013 / Accepted 19 August 2013 / Published 15 November 2013)

Abstract

Kinetic damping in linear gyrokinetic (GK) Vlasov simulations is found to exhibit a bifurcation at the collisionality βc = βc∗, above which, i.e. βc > βc∗, the damping is represented by a Landau eigenmode in velocity space, while below which, i.e. βc < βc∗, 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 βc∗ numerically and found that the stabilization effect works properly beyond the recurrence time even in the phase mixing regime across βc = βc∗.

Keywords

gyrokinetics, Landau damping, Case-van Kampen eigenmode, mode coupling

DOI: 10.1585/pfr.8.1303151

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This paper may be cited as follows:

Paul P. HILSCHER, Kenji IMADERA, Jiquan LI and Yasuaki KISHIMOTO, Plasma Fusion Res. 8, 1303151 (2013).