2025-12-10 核融合科学研究所
図１ プラズマ中の乱流が担う「一人二役」のイメージ図。
（上）離れた領域を同時につなぐ「つなぎ役」の乱流は、選手たちが声を掛け合って素早くパスを回す動作に相当し、プラズマ内部で遠隔の領域を瞬時に結びつけて熱の広がりを加速させている。
（下）熱を実際に外側へ運ぶ「運搬役」の乱流は、ボール（熱）を抱えて前へ走るアメフト選手のように、時間をかけて広がりながらプラズマの温度分布を形づくる。
＜関連情報＞
磁場閉じ込めプラズマにおける局所的乱流と非局所的乱流の共存の実験的同定 Direct observation of coexisting local and nonlocal turbulence in a magnetically confined plasma
Naoki Kenmochi,Katsumi Ida,Tokihiko Tokuzawa,Yoshinori Mizuno,Ryo Yasuhara,Hisamichi Funaba,Hiyori Uehara,Daniel J. Den Hartog,Mikirou Yoshinuma,Yuki Takemura,Hiroe Igami,Ryoma Yanai & Toshiki Takeuchi
Communications Physics Published:10 December 2025
DOI:https://doi.org/10.1038/s42005-025-02454-x
Abstract
Observing mediating structures in nonlocal transport is a cross-disciplinary challenge that spans disordered materials and turbulent fluids. The difficulty stems from the transient nature of mediators and nonlocal responses to probes, which renders indirect diagnostic and numerical simulations the most commonly used probing strategies. This study introduces a direct method using high-resolution spatiotemporal diagnostics in magnetically confined plasma to isolate two turbulence regimes: high-frequency local turbulence, which scales with temperature gradients and carries heat flux, and low-frequency nonlocal turbulence, which acts as a mediator and rapidly links distant regions. We observe temporal ordering as follows: immediately after heating, nonlocal turbulence appears, followed by local turbulence carrying the heat pulse. Shorter heating shifts the balance toward the nonlocal component. The impact of the mediator is quantified by the scaling v ∝ s−1.06 between the heat-pulse speed v and duration s, demonstrating that stronger departures from steady state enhance nonlocal transport. Correspondingly, the intensity ratio of the nonlocal-to-local turbulence increases as s shortens. This direct observation of nonlocal transport offers insights into mediator-enabled pathways and advances the understanding of nonlocal dynamics.
