Enhancement and suppression of turbulence by energetic-particle-driven geodesic acoustic modes.
Enhancement and suppression of turbulence by energetic-particle-driven geodesic acoustic modes.
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DOI：
10.1038/s41598-017-17011-y
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发表时间：
2017-12-01
影响因子：
4.6
通讯作者：
Itoh SI
中科院分区：
文献类型：
--
作者：
Sasaki M;Itoh K;Hallatschek K;Kasuya N;Lesur M;Kosuga Y;Itoh SI
提出了一种新的能量粒子驱动测地声学模式（EGAM）增强湍流的机制。利用波动方程研究了相空间中漂移波型湍流的动力学行为。考虑了存在输运障碍时的空间非均匀湍流。我们发现EGAM对湍流团的捕获是决定抑制或增强湍流的关键参数。在湍流不稳定的区域，EGAM抑制湍流。与此相反，在稳定区域，EGAM陷阱的湍流块，并携带它们通过传输障碍，使湍流可以增强。EGAM捕获的湍流可以独立于密度和温度梯度传播，这导致非Fickian输运。因此，在湍流动力学中，除了局域群速度和湍流传播速度之外，还出现了一个新的全局特征速度--高斯光束的相速度。由于这些效应，EGAM可以恶化传输障碍并显著影响湍流。这份手稿提供了一个基础，考虑是否相干波打破或加强运输障碍。
We propose a novel mechanism of enhancement of turbulence by energetic-particle-driven geodesic acoustic modes (EGAMs). The dynamics of drift-wave-type turbulence in the phase space is investigated by wave-kinetic equation. Spatially inhomogeneous turbulence in the presence of a transport barrier is considered. We discovered that trapping of turbulence clumps by the EGAMs is the key parameter that determines either suppress or enhance turbulence. In regions where turbulence is unstable, EGAM suppresses the turbulence. In contrast, in the stable region, EGAM traps clumps of turbulence and carries them across the transport barrier, so that the turbulence can be enhanced. The turbulence trapped by EGAMs can propagate independent of the gradients of density and temperature, which leads to non-Fickian transport. Hence, there appear a new global characteristic velocity, the phase velocity of GAMs, for turbulence dynamics, in addition to the local group velocity and that of the turbulence spreading. With these effect, EGAMs can deteriorate transport barriers and affect turbulence substantially. This manuscript provides a basis to consider whether a coherent wave breaks or strengthen transport barriers.
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