In strong electromagnetic regimes, gyrokinetic simulations have linked a substantial ion-scale turbulence stabilization to the presence of supra-thermal particles, capturing qualitatively well the experimental observations in different devices worldwide. An explanation for the underlying physical mechanism responsible for the fast-ion-induced turbulent transport reduction observed in the numerical simulations has been proposed only recently by Di Siena et al. (Nucl. Fusion, vol. 59, 2019, p. 124001; Nucl. Fusion, vol. 60, 2020, p. 089501). It involves a nonlinear cross-scale coupling (nonlinear interaction involving different modes at different wavenumbers) between ion-temperature-gradient and marginally stable Alfvén eigenmodes, which in turn increases zonal flow activity. In view of an optimization of this turbulence-stabilizing effect, the key parameters controlling the nonlinear cross-scale coupling are here identified. At the same time, these findings provide useful insights for reduced-turbulence models and integrative approaches, which might be trained on the results presented in this paper to grasp the underlying physics and the parameter scaling of the beneficial effects of fast particles on plasma turbulence.

中文翻译：

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快离子与离子温度梯度等离子体湍流之间的非线性电磁相互作用

在强电磁状态下，陀螺动力学模拟已将大量的离子尺度湍流稳定性与超热粒子的存在联系起来，从而在全球范围内很好地捕捉到了不同设备中的实验观察结果。直到最近，Di Siena 才提出了对数值模拟中观察到的导致快速离子诱导的湍流输运减少的潜在物理机制的解释等。(核。融合, 卷。2019 年，第 59 期，第 59 页。124001;核。融合, 卷。2020 年 60 月，第 60 页。089501）。它涉及离子-温度-梯度和边缘稳定的 Alfvén 特征模式之间的非线性跨尺度耦合（涉及不同波数的不同模式的非线性相互作用），这反过来又增加了纬向流动活动。鉴于这种湍流稳定效应的优化，这里确定了控制非线性跨尺度耦合的关键参数。同时，这些发现为减少湍流模型和综合方法提供了有用的见解，可以根据本文提出的结果进行训练，以掌握快速粒子对等离子体湍流的有益影响的基本物理学和参数缩放。