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Bifurcation of drift wave turbulence trapping by zonal flows near density limit

M. Sasaki, G. Yatomi, Y. Onuki, T. Kobayashi, Y. Kawachi, F. Kin, K. Itoh2026年2月Nuclear FusionIF 3出版社

We investigate drift wave—zonal flow interactions near the density limit and demonstrate transitions of turbulence trapping states. Nonlinear simulations of the modified Hasegawa–Wakatani model reveal two robust types of turbulence energy localization: valley-trapping near zonal flow troughs at small adiabaticity (hydrodynamic regime) and hill-trapping near crests at large adiabaticity (adiabatic regime). Around the transition, turbulence exhibits bistability, dynamically switching between valley- and hill-trapping, and also shows indications of multi-stable behavior depending on the adiabaticity. The Lagrangian auto-correlation time of turbulence changes markedly across the bifurcation between the trapping states, indicating that turbulent vortices become long-lived in the adiabatic limit and short-lived in the hydrodynamic limit. Eigenmode analysis reproduces these patterns and shows that the selection is governed by the relative magnitude of the drift wave phase velocity and the zonal flow amplitude. These findings provide a simple selection rule for turbulence energy localization and offer new insight into drift wave—zonal flow dynamics in regimes relevant to the density limit.

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Zonal flowDrift wavesDensity limitDrift wave turbulence

AIによる論文要約

密度限界近傍における帯状流によるドリフト波乱流捕捉の分岐
JA核融合プラズマの乱流や密度限界に興味のある研究者や大学院生。特に、ドリフト波-帯状流相互作用の基礎メカニズムを理解したい方に有用です。#核融合 #プラズマ乱流 #帯状流 #密度限界 #ドリフト波
LLM向け: {"Title": "密度限界近傍における帯状流によるドリフト波乱流捕捉の分岐", "Authors": "指定なし", "Research Objective…

核融合プラズマの密度限界近くでは、ドリフト波乱流と帯状流の相互作用が重要です。本研究では、修正長谷川-若谷モデルを用いた非線形シミュレーションにより、乱流エネルギーが帯状流の谷(低流速部)または丘(高流速部)に捕捉される2つの状態を発見しました。断熱性が小さいと谷捕捉、大きいと丘捕捉が起こり、その中間では双安定性を示します。モード解析により、捕捉状態はドリフト波の位相速度と帯状流振幅の比で決まることがわかりました。この結果は、密度限界近くのプラズマ乱流の理解に役立ちます。

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