Observations of abrupt changes in the fluctuation spectrum on LMD-U

Arakawa, Hiroyuki; Kamataki, Kunihiro; Inagaki, S.; Maruta, Takashi; Nagashima, Yoshihiko; Yamada, Teppei; Shinohara, Shunjiro; Terasaka, Kenichiro; Sugita, S.; Yagi, M.; Kasuya, Naohiro; Fujisawa, A.; Itoh, Sanae–I.; Itoh, K.

doi:10.1088/0741-3335/51/8/085001

Cited by 14 publications

(18 citation statements)

References 29 publications

(35 reference statements)

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“…In the region having a intermediate magnetic field and a intermediate neutral pressure, the occurrence regions of the two states approach each other. In- terestingly, an abrupt and spontaneous transition between the two nonlinear turbulence states occurs in this parameter regime [21,22]. The existence of the transition region at which the two regions are adjacent may imply that the present choice of the threshold values is valid.…”

Section: Discussion and Summarymentioning

confidence: 91%

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Phenomenological Classification of Turbulence States in Linear Magnetized Plasma PANTA

Kobayashi

Inagaki

Sasaki

et al. 2017

Plasma and Fusion Research

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Changing the experimental conditions such as the neutral pressure and the magnetic field strength provides a drastic change in the turbulence states in linear magnetized helicon plasmas. In order to define the turbulence states and their occurrence region a throughout parameter scan in the two-dimensional parameter space was performed. The classification of the turbulence states is carried out phenomenologically based on the turbulence spectrum and the waveform.

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Section: Discussion and Summarymentioning

confidence: 91%

“…Dynamic competition between the solitary wave and the zonal flow type oscillation was also studied [15,19,20]. An abrupt and spontaneous transition between the solitary wave state and the streamer state was also observed [21,22].…”

Section: Introductionmentioning

confidence: 99%

Phenomenological Classification of Turbulence States in Linear Magnetized Plasma PANTA

Kobayashi

Inagaki

Sasaki

et al. 2017

Plasma and Fusion Research

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“…Interaction between separate components of the DW-ZF turbulence is found to affect the turbulent transport dynamics. Experimental studies in both linear and toroidal devices show that the state of turbulence changes with the magnetic field (CSDX), 7,8 the filling gas pressure (LMDU), 9 and the radial electric field (KIWI). 10 Shearing of the DW structures leads to an energy transfer between low frequency fluctuations and vortices with finite azimuthal mode numbers, including m $ 0 zonal flows.…”

Section: For a Detailed Review)mentioning

confidence: 99%

Modelling enhanced confinement in drift-wave turbulence

et al. 2017

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The results of modeling studies of an enhanced confinement in the drift wave turbulent plasma of the CSDX linear device are presented. The mechanism of enhanced confinement is investigated here using a reduced 1D, time-dependent model, which illustrates the exchange of enstrophy between two disparate scale structures: the mesoscale flow and profile, and the turbulence intensity fields. Mean density, mean vorticity, and turbulent potential enstrophy are the variables for this model. Total potential enstrophy is conserved in this model. Vorticity mixing occurs on a scale length related to an effective Rhines' scale of turbulence, and shrinks as both density and vorticity gradients steepen. Numerical results obtained from solution of the model agree well with the experimental data from CSDX showing: (i) a steepening of the mean density profile, indicating a radial transport barrier formation, (ii) the development of a radially sheared azimuthal flow velocity that coincides with the density steepening and initiates a turbulence quench, and (iii) negative Reynolds work values, indicating that fluctuations drive the shear flow. These observations as the magnitude of the magnetic field B increases are recovered using purely diffusive expressions for the vorticity and density fluxes. A new dimensionless turbulence parameter R DT-defined as the ratio of the integrated potential enstrophy transfer from turbulence to the flow, to the integrated potential enstrophy production due to relaxation of the density gradient is introduced as a turbulence collapse indicator that detects when the enhanced confinement state is triggered. Published by AIP Publishing.

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“…Recently, dynamical responses of the turbulent plasmas to an externally imposed perturbations have been investigated, such as heating [13], biasing [14], and others. In addition, the dynamical evolution of turbulence spectra is now possibly measured in detail [15,16], and provides a new area to study the nonlinear interactions in turbulence quantitatively. These evolutions urge to study the dynamical response of the turbulent driven structure by using a numerical turbulence simulation.…”

Section: Introductionmentioning

confidence: 99%

Dynamical Response of Turbulent Structures in Cylindrical Magnetized Plasmas

Sasaki

Kasuya

Itoh

et al. 2014

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

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Dynamical response of the streamer near a critical condition where the streamer disappears is investigated by using a three dimensional fluid simulation. The gradual change of the global control parameter is given to the plasma. When the control parameter approaches the critical condition, the phase mismatch between the drift waves (which form the streamer) and the mediator mode increases abruptly, finally loosing the nonlinear matching condition. The eigenmode is also modified after the transition from streamer to the other state occurs. The phase relation is much sensitive compared to the change of amplitude, and could be observed even by a one-point measurement.

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Observations of abrupt changes in the fluctuation spectrum on LMD-U

Cited by 14 publications

References 29 publications

Phenomenological Classification of Turbulence States in Linear Magnetized Plasma PANTA

Phenomenological Classification of Turbulence States in Linear Magnetized Plasma PANTA

Modelling enhanced confinement in drift-wave turbulence

Dynamical Response of Turbulent Structures in Cylindrical Magnetized Plasmas

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