Anatomy of plasma turbulence
Anatomy of plasma turbulence
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DOI：
10.1038/nphys1029
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发表时间：
2008-09-01
期刊：
影响因子：
19.6
通讯作者：
Itoh, Kimitaka
中科院分区：
文献类型：
--
作者：
Yamada, Takuma;Itoh, Sanae-I.;Itoh, Kimitaka
湍流是流体和等离子体的一种状态，其中发生包括级联到更精细尺度的非线性相互作用，以产生混沌结构和动力学（1）。然而，湍流可以产生全局结构（2），如发电机磁场，纬向流（3），传输障碍，增强传输和淬火传输。因此，在湍流中，多尺度现象在空间和时间上共同演化，等离子体湍流的特征已经在实验室中被研究（4-10），作为现代和历史的科学之谜。在这里，我们通过使用包括双谱的非线性谱分析报告了波数-频域中等离子体湍流的解剖特征（11）。首先，等离子体湍流的形成可以看作是满足线性色散关系的少数不可约母模的非线性相互作用的结果。第二，这里强调的发现是第一次识别出流光（漂移波聚束的状态（12，13）），它会降低磁约束聚变等离子体的质量（14，15）。流光是一个poloidally本地化，径向拉长的全球结构，寿命长于特征湍流相关时间，我们的研究结果表明，流光产生的结果的非线性凝聚，或非线性锁相的主要三重态模式。
Turbulence is a state of fluids and plasma where nonlinear interactions including cascades to finer scales take place to generate chaotic structure and dynamics(1). However, turbulence could generate global structures(2), such as dynamo magnetic field, zonal flows(3), transport barriers, enhanced transport and quenching transport. Therefore, in turbulence, multiscale phenomena coevolve in space and time, and the character of plasma turbulence has been investigated in the laboratory(4-10) as a modern and historical scientific mystery. Here, we report anatomical features of the plasma turbulence in the wavenumber-frequency domain by using nonlinear spectral analysis including the bi-spectrum(11). First, the formation of the plasma turbulence can be regarded as a result of nonlinear interaction of a small number of irreducible parent modes that satisfy the linear dispersion relation. Second, the highlighted finding here, is the first identification of a streamer ( state of bunching of drift waves(12,13)) that should degrade the quality of plasmas for magnetic confinement fusion(14,15). The streamer is a poloidally localized, radially elongated global structure that lives longer than the characteristic turbulence correlation time, and our results reveal that the streamer is produced as the result of the nonlinear condensation, or nonlinear phase locking of the major triplet modes.