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TJ-II:Turbulence: Difference between revisions
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<ref>B.Ph. van Milligen et al, Wavelet bicoherence: a new turbulence analysis tool, Phys. Plasmas '''2''', 8 (1995) 3017</ref> | <ref>B.Ph. van Milligen et al, Wavelet bicoherence: a new turbulence analysis tool, Phys. Plasmas '''2''', 8 (1995) 3017</ref> | ||
<ref>B.Ph. van Milligen et al, Statistically robust linear and non-linear wavelet analysis applied to plasma edge turbulence, Rev. Sci. Instrum. '''68''' (1997) 967</ref> | <ref>B.Ph. van Milligen et al, Statistically robust linear and non-linear wavelet analysis applied to plasma edge turbulence, Rev. Sci. Instrum. '''68''' (1997) 967</ref> | ||
<ref>P.H. Diamond et al, In search of the elusive zonal flow using cross-bicoherence analysis, Phys. Rev. Lett. '''84''', 12 (2000) 4842</ref> | |||
<ref>B.Ph. van Milligen et al, Bicoherence during confinement transitions in the TJ-II stellarator, Nucl. Fusion '''48''' (2008) 115003</ref> | <ref>B.Ph. van Milligen et al, Bicoherence during confinement transitions in the TJ-II stellarator, Nucl. Fusion '''48''' (2008) 115003</ref> | ||
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and the Bohm scaling of plasma confinement might be explained on the basis of profile self-regulation in the framework of the [[Self-Organised Criticality]] paradigm. This paradigm predicts that transport is regulated by avalanches, which would generate self-similar behaviour in space and time of the turbulent data. | and the Bohm scaling of plasma confinement might be explained on the basis of profile self-regulation in the framework of the [[Self-Organised Criticality]] paradigm. This paradigm predicts that transport is regulated by avalanches, which would generate self-similar behaviour in space and time of the turbulent data. | ||
In order to test this hypothesis, one could determine the shape of the autocorrelation function (ACF) of turbulent signals. | In order to test this hypothesis, one could determine the shape of the autocorrelation function (ACF) of turbulent signals. | ||
<ref>B.A. Carreras et al, Fluctuation-induced flux at the plasma edge in toroidal devices, Plasma Physics '''3''' (7) (1996) 2664</ref> | |||
<ref>B.A. Carreras et al, Self-similarity properties of the probability distribution function of turbulence-induced particle fluxes at the plasma edge, Phys. Rev. Lett. '''83''' (1999) 3653</ref> | |||
<ref>B.A. Carreras, Intermittency of plasma edge fluctuation data: Multifractal analysis, Phys. Plasmas, '''7''', 8 (2000) 3278</ref> | |||
<ref>C. Hidalgo et al, Empirical similarity in the probability density function of turbulent transport in the edge plasma region in fusion plasmas, Plasma Phys. Control. Fusion '''44''' (2002) 1557</ref> | |||
<ref>B.Ph. Van Milligen et al, Additional evidence for the universality of turbulent fluctuations and fluxes in the scrape-off layer region of fusion plasmas, Physics of Plasmas '''12''' (2005) 052507</ref> | <ref>B.Ph. Van Milligen et al, Additional evidence for the universality of turbulent fluctuations and fluxes in the scrape-off layer region of fusion plasmas, Physics of Plasmas '''12''' (2005) 052507</ref> | ||
Unfortunately, the most revealing information is present in the tail of the distribution (i.e., well beyond the correlation time), where statistics are generally poor. | Unfortunately, the most revealing information is present in the tail of the distribution (i.e., well beyond the correlation time), where statistics are generally poor. | ||
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The repeated occurrence of values of H differing significantly from the value corresponding to random noise (H = 0.5) in all machines points to a universal aspect of the underlying turbulence. Further, the degree of self-similarity detected implies the existence of long-range correlations (with respect to the correlation time). | The repeated occurrence of values of H differing significantly from the value corresponding to random noise (H = 0.5) in all machines points to a universal aspect of the underlying turbulence. Further, the degree of self-similarity detected implies the existence of long-range correlations (with respect to the correlation time). | ||
<ref>B.A. Carreras et al, Long-range time correlations in plasma edge turbulence, Phys. Rev. Lett. '''80''', (1998) 4438</ref> | |||
<ref>B.A. Carreras et al, Self-similarity of the plasma edge fluctuations, Phys. Plasmas '''5''', 10 (1998) 3632</ref> | |||
<ref>B.A. Carreras et al, Long-range time dependence in the cross-correlation function, Phys. Plasmas '''6''', 2 (1999) 485</ref> | |||
<ref>B.A. Carreras et al, Experimental evidence of long-range correlation and self-similarity in plasma fluctuations, Phys. Plasmas '''6''', 5 (1999) 1885</ref> | |||
In this framework, an important technique is the quiet-time analysis. | In this framework, an important technique is the quiet-time analysis. | ||
<ref>R. Sánchez et al, Quiet-time statistics: A tool to probe the dynamics of self-organized-criticality systems from within the strong overlapping regime, Phys. Rev. E, '''66''' (2002) 036124</ref> | |||
<ref>R. Sánchez et al, Quiet-time statistics of electrostatic turbulent fluxes from the JET tokamak and the W7-AS and TJ-II stellarators, Phys. Rev. Lett. '''90''', 18 (2003)</ref> | |||
<ref>V.E. Lynch et al, Determination of long-range correlation by quiet-time statistics, Phys. Plasmas '''12''' (2005) 052304</ref> | <ref>V.E. Lynch et al, Determination of long-range correlation by quiet-time statistics, Phys. Plasmas '''12''' (2005) 052304</ref> | ||
=== Turbulent structures === | === Turbulent structures === | ||
An important effort has also been made to classify and | An important effort has also been made to identify and classify turbulence, | ||
<ref>C. Hidalgo et al, Intermittency and structures in edge plasma turbulence, Comptes Rendus Physique '''7''', 6 (2006) 679</ref> | <ref>E. Sánchez et al, Statistical characterization of fluctuation waveforms in the boundary region of fusion and non-fusion plasmas, Phys. Plasmas '''7''', 5 (2000) 1408</ref> | ||
<ref>M.A. Pedrosa et al, Role of rational surfaces on fluctuations and transport in the plasma edge of the TJ-II stellarator, Czechoslovak Journal of Physics, '''50''', 12 (2000) 1463</ref> | |||
<ref>I. García-Cortés et al, Turbulent transport studies in the JET edge plasmas in limiter configuration, Plasma Phys. Control. Fusion '''42''' (2000) 389</ref> | |||
<ref>M.A. Pedrosa et al, Edge turbulence during limiter biasing experiments in the TJ-II stellarator, Czechoslovak Journal of Physics, '''53''' (2003) 877</ref> | |||
<ref>C. Hidalgo et al, Intermittency and structures in edge plasma turbulence, Comptes Rendus Physique '''7''', 6 (2006) 679</ref> | |||
to analyse its spectra, | |||
<ref>M. A. Pedrosa et al, Empirical similarity of frequency spectra of the edge plasma fluctuations in toroidal magnetic confinement systems, Phys. Rev. Lett. '''82''' (1999) 3621</ref> | |||
<ref>B.A. Carreras et al, Characterization of the frequency ranges of the plasma edge fluctuation spectra, Phys. Plasmas '''6''', 12 (1999) 4615</ref> | |||
<ref>M. A. Pedrosa et al, Studies of spectra of the edge plasma fluctuations in toroidal magnetic confinement systems, J. Plasma Fusion. Res. SERIES, '''2''' (1999) 77</ref> | |||
to determine its relation with local plasma parameters (such as gradients), | |||
<ref>B. Gonçalves et al, Experimental investifation of dynamical coupling between density gradients, radial electric fields and turbulent transport in the JET plasma boundary region, Nucl. Fusion '''42''' (2002) 1205</ref> | |||
and to visualise turbulent structures. | |||
<ref>J. A. Alonso et al, Two-Dimensional Turbulence Analysis Using High-Speed Visible Imaging in TJ-II Edge Plasmas, Fusion Science and Technology '''50''', 2 (2006) 301</ref> | <ref>J. A. Alonso et al, Two-Dimensional Turbulence Analysis Using High-Speed Visible Imaging in TJ-II Edge Plasmas, Fusion Science and Technology '''50''', 2 (2006) 301</ref> | ||
<ref>J.A. Alonso et al, Impact of different confinement regimes on the two-dimensional structure of edge turbulence, Plasma Phys. Control. Fusion '''48''' (2006) B465</ref> | <ref>J.A. Alonso et al, Impact of different confinement regimes on the two-dimensional structure of edge turbulence, Plasma Phys. Control. Fusion '''48''' (2006) B465</ref> | ||