Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

Birkenmeier, G.; Ramisch, M.; Schmid, Bernhard; Stroth, U.

doi:10.1103/physrevlett.110.145004

Cited by 41 publications

(44 citation statements)

References 36 publications

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“…Moreover, these findings are also consistent with previous experimental results 11,[13][14][15][16][17][18][19][20][21]41,43,45 obtained with a variety of devices, in which variations in cross-correlation terms in the presence of mean shear flows or ZFs played comparable or even more critical role in suppressing transport, in contrast with the suppression of fluctuation intensities. However, one should realize that according to existing experiments, focusing on this topic of transport reduction induced by shear flows, including our observations described above, incompatible mechanisms have been separately inferred to be dominant, especially as we focus on the contribution of each spectral component of the flux, Eq.…”

Section: Discussionsupporting

confidence: 93%

Observation of fluctuation-driven particle flux reduction by low-frequency zonal flow in a linear magnetized plasma

et al. 2015

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Low-frequency zonal flow (ZF) has been observed in a linear magnetic plasma device, exhibiting significant intermittency. Using the conditional analysis method, a time-averaged fluctuationinduced particle flux was observed to consistently decrease as ZF increased in amplitude. A dominant fraction of the flux, which is driven by drift-wave harmonics, is reversely modulated by ZF in the time domain. Spectra of the flux, together with each of the related turbulence properties, are estimated subject to two conditions, i.e., when potential fluctuation series represents a strong ZF intermittency or a very weak ZF component. Comparison of frequency-domain results demonstrates that ZF reduces the cross-field particle transport primarily by suppressing the density fluctuation as well as decorrelating density and potential fluctuations. V C 2015 AIP Publishing LLC.

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Section: Discussionsupporting

confidence: 93%

Observation of fluctuation-driven particle flux reduction by low-frequency zonal flow in a linear magnetized plasma

et al. 2015

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“…In this article blob refers to a coherent structure with high density with respect to the surrounding fluctuation level. It is widely accepted that poloidal shear flows increase the particle and energy confinement in fusion devices [2][3][4][5][6]. Recently, the extraordinary role of shear layers for blob generation has been identified [7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Turbulent transport across shear layers in magnetically confined plasmas

et al. 2014

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Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatialtemporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

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“…PACS number(s): 47.27.−i The problem of low-to-high confinement transition (L-H transition) in magnetized plasmas has persisted as a subject of vivid research since its observation in 1982 [1][2][3]. The paradigm, mainly elaborated by Diamond and coworkers, deals with the self-consistent interaction of small-scale plasma fluctuations and sheared macroscopic flows [4][5][6][7][8]12]. Critical gradients of plasma parameters (density and temperature) can drive unstable waves called drift waves, leading to a turbulent system of nonlinearly interacting modes.…”

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confidence: 99%

Experimental confirmation of self-regulating turbulence paradigm in two-dimensional spectral condensation

et al. 2014

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Turbulent transport in magnetic fusion plasmas can be significantly suppressed by Reynolds-stress-induced zonal flows, allowing effective plasma confinement. We present experimental evidence of spatiotemporal correlation between small-scale turbulence-induced Reynolds stress and large-scale zonal flow production in the E×B driven hydrodynamic spectral condensation. We show that Reynolds stress is generated effectively by anisotropic vorticity structures possessing collective tilt angle. The maximum amplitude of the tilt, the Reynolds stress, and the mean zonal flow production coincide with the transition time of the velocity field, indicating a key role of turbulence-induced Reynolds stress in the condensation of the flow. The analysis of the energy transfer between turbulence and zonal flow shows coherent oscillations with π/2 phase delay, thus indicating a predator-prey-like interaction between zonal flow and turbulence.

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Experimental Evidence of Turbulent Transport Regulation by Zonal Flows

Cited by 41 publications

References 36 publications

Observation of fluctuation-driven particle flux reduction by low-frequency zonal flow in a linear magnetized plasma

Observation of fluctuation-driven particle flux reduction by low-frequency zonal flow in a linear magnetized plasma

Turbulent transport across shear layers in magnetically confined plasmas

Experimental confirmation of self-regulating turbulence paradigm in two-dimensional spectral condensation

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