Intermittency in tokamak edge turbulence: An artifact of kurtosis analysis

Journal Article · Thu Jun 01 04:00:00 EDT 1995 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.871285· OSTI ID:172049

Sethia, G C; Chenna Reddy, D ^[1]

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1. Institute for Plasma Research, Bhat, Gandhinagar 382 424 (India)

Kurtosis or flatness factor of an experimental time series is considered to be one of the important computed parameters in turbulence studies. The analysis itself is of a simple nature but like any other statistical analysis it demands extreme caution in the absence of which one is prone to draw false conclusions. An earlier kurtosis based statistical analysis [Phys. Rev. Lett. {bold 69}, 1375 (1992)] on the reported {ital first} measurement of intermittency in tokamak edge turbulence using density and potential fluctuation data has been found to be questionable on a number of counts (``Comment`` submitted to Phys. Rev. Lett.). This has necessitated a detailed reanalysis of the same data which has now been carried out and the results are presented in this paper. It is found that most of the density datasets and all the potential datasets exhibit a significant peak in their autospectra at about 4--6 kHz and all other datasets with significant non-Gaussianity are found to be either having plasma current associated high amplitude transients or are found to be nonstationary due to a trend in the variance. The datasets are close to Gaussian with kurtosis values approaching zero if these factors are properly taken care of. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

• OSTI ID: 172049
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 6 Vol. 2; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ADITYA TOKAMAK
FLUCTUATIONS
GAUSSIAN PROCESSES
TIME-SERIES ANALYSIS
TOKAMAK DEVICES
TURBULENCE