On the bicoherence analysis of plasma turbulence

Itoh, K.; Nagashima, Yoshihiko; Itoh, Sanae I.; Diamond, P. H.; Fujisawa, A.; Yagi, M.; Fukuyama, A.

doi:10.1063/1.2062627

Cited by 51 publications

(62 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast to the cases of zonal flows and GAMs, the coupling between the microscopic fluctuations indicates the randomly varying biphase. This is consistent with the theoretical prediction of nonlinear interaction of drift wave turbulence [18]. Structural transition in turbulent plasmas has been known [1,7], and a new type of it has been pointed out by introducing the coupling between micro, meso and macro perturbations [33,34].…”

Section: Measurement Of Nonlinear Interactionsupporting

confidence: 74%

See 1 more Smart Citation

On Imaging of Plasma Turbulence

Itoh

Fujisawa

Nagashima

et al. 2007

Plasma and Fusion Research

Self Cite

View full text Add to dashboard Cite

We discuss aspects of imaging of plasma turbulence, taking the standpoint that the imaging is a path for induction of law from complex signals. An example of induction of symbol from signals is illustrated. Then the image of plasma turbulence is extended, putting an emphasis on the identification of the nonlinear interaction in turbulence. By employing the bipspectral method, magnitudes of interactions among excited modes are estimated. Interactions between microscopic turbulence and large-scale structures are demonstrated, providing our understanding of structure formation in turbulent plasmas.

show abstract

Section: Measurement Of Nonlinear Interactionsupporting

confidence: 74%

“…Thus, the bicoherence represents the nonlinear interactions. The bispectrum in turbulent plasmas has been theoretically evaluated in [18]. The studies on nonlinear interaction among drift wave turbulence and zonal flows have been widely reported.…”

Section: Measurement Of Nonlinear Interactionmentioning

confidence: 99%

On Imaging of Plasma Turbulence

Itoh

Fujisawa

Nagashima

et al. 2007

Plasma and Fusion Research

Self Cite

View full text Add to dashboard Cite

show abstract

“…In practice, quantitative meanings of the squared bicoherence in plasma turbulence are also presented in a theory paper [22]. The total bicoherence, a summation of the squared bicoherence, is convenient for representing the nonlinear contribution from many modes to a single mode, and is defined as…”

Section: Bispectral Analysismentioning

confidence: 99%

“…[22]. A normalized electrostatic potential, φ = (eφ/T e )L n /ρ s , is introduced, whereφ is the electrostatic potential fluctuation, ρ s is the ion gyro-radius at electron temperature, and L n is the density gradient scale length.…”

Section: Comparison With Theoretical Predictionsmentioning

confidence: 99%

See 1 more Smart Citation

Experimental Study of Nonlinear Processes in Edge Turbulence of Toroidal Plasmas

Nagashima

Hoshino

Nagaoka

et al. 2006

Plasma and Fusion Research

View full text Add to dashboard Cite

This paper presents experimental studies of nonlinear processes between meso-scale structures and turbulent fluctuations, by use of bispectral analysis, in the edge region of toroidal plasmas. In ohmically heated plasmas of the JFT-2M tokamak, the drift wave-zonal flow system is investigated by observation of the potential fluctuations. The total bicoherence is composed of two components, i.e., the peak at the geodesic acoustic mode (GAM) frequency and broadband distribution. The biphase is also obtained, which indicates the phase angle of coherent interaction between GAM oscillations and broadband fluctuations. Bispectral functions (e.g., magnitude and phase) give an order-of-estimate agreement for the drift wave-zonal flow systems. Bicoherence analysis is also applied to the edge plasmas of the high-confinement mode (H-mode) of the Compact Helical System (CHS). In the case of CHS plasmas, nonlinear couplings in a system composed of coherent global magneto-hydrodynamic (MHD) oscillations and broadband fluctuations (up to hundreds kHz range) have been observed. Bispectral analysis enhances our understanding of the self-regulation systems of various toroidal plasmas in which strong turbulence and meso-scale structures coexist.

show abstract

Coherent structure generated in the boundary layer of a laboratory‐created ionospheric depletion

Liu

Cao

et al. 2014

Geophysical Research Letters

View full text Add to dashboard Cite

Laboratory experiments have been conducted to simulate the boundary processes of ionospheric depletion. The ionospheric depletion was modeled through releasing depletion chemical (SF6) into the ambient plasmas. These plasmas were segregated into two regions by a boundary layer of width electric scale length. In the localized boundary layer, the electron density decreased sharply that yielded steep density gradients. Meanwhile, the floating potential increased in the time scales of the lower hybrid (LH) period, which produced strong sheared electron flows. The shear frequency ωs=VE/LE, which characterizes the sheared flow, is much larger than the LH frequency ωLH. A coherent structure was observed when the floating potential fluctuations were analyzed using digital spectral analysis techniques. Comparison with the theory indicated that the structure is driven by the electron‐ion hybrid instability which is generated owing to the nonlinear coupling between the electron density gradient and the sheared electron flow. Our results are important to study the early phase nonlinear evolution of the ionospheric depletion, especially in the development of plasma irregularities and turbulence in the boundary layer.

show abstract

On the bicoherence analysis of plasma turbulence

Cited by 51 publications

References 21 publications

On Imaging of Plasma Turbulence

On Imaging of Plasma Turbulence

Experimental Study of Nonlinear Processes in Edge Turbulence of Toroidal Plasmas

Coherent structure generated in the boundary layer of a laboratory‐created ionospheric depletion

Contact Info

Product

Resources

About