发表机构
Chung-Ang University（中央大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过KSTAR FIRE模式的全局回旋动力学模拟，发现快离子增强带状流与剪切层，使热通量随离子温度梯度增加而减小，偏离菲克定律，表明FIRE模式可能是一种分岔到新输运机制的现象。
AI 中文摘要
带状流组织可以改变热通量与温度梯度之间的关系，但快离子如何影响这种组织及伴随的输运响应仍鲜有表征。我们基于KSTAR快离子调控增强（FIRE）模式，使用非线性、全局回旋动力学模拟，在五个初始主离子温度梯度下的剖面弛豫过程中，比较了有快离子与无快离子的情况。我们观察到，快离子诱导出更大的带状流和剪切率幅度，并伴随持久的剪切层。在基于实验的参考剖面中，这些剪切层与温度梯度波纹共存，后者在定性上与$E\ imes B$阶梯结构一致。当存在快离子时，内向和外向离子热通量在不同半径处共存，这导致平均热通量小于无快离子时的值。这种离子热输运的重新分布可能有助于理解FIRE模式中观察到的改善的离子约束。特别地，我们注意到在存在快离子时出现类转变响应，即随着离子温度梯度增加，热通量反而减小，这与无快离子时传统的菲克定律趋势相反。这种偏离菲克定律的行为表明，FIRE模式可能代表向一种独特输运 regime 的分岔，而非L模式的连续高性能延伸。这些发现强调了在评估快离子对离子热输运影响时，初始温度梯度和全局带状流组织的重要性。
英文摘要
Zonal-flow organization can modify the relation between heat flux and temperature gradient, but how fast ions affect this organization and the accompanying transport response remains less well characterized. We use nonlinear, global gyrokinetic simulations based on KSTAR fast-ion-regulated enhancement (FIRE) mode to compare cases with and without fast ions during profile relaxation across five initial main-ion temperature gradients. We observe that fast ions induce larger zonal-flow and shearing-rate amplitudes, together with persistent shear layers. At the reference profile based on the experiment, these shear layers coexist with temperature-gradient corrugations qualitatively consistent with $E\times B$ staircases. When fast ions are present, inward and outward ion heat fluxes coexist at different radii, which causes the average heat flux to be smaller than when fast ions are absent. This redistribution of ion heat transport may be relevant to understanding the improved ion confinement observed in FIRE mode. In particular, we note a transition-like response in the presence of fast ions, whereby the heat flux decreases as the ion-temperature gradient increases, in contrast to the conventional Fick's law trend without fast ions. This behavior that deviates from Fick's law suggests that FIRE mode may represent a bifurcation to a distinct transport regime rather than a continuous high-performance extension of L-mode. These findings highlight the importance of the initial temperature gradient and global zonal-flow organization when assessing fast-ion effects on ion heat transport.
