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Title: Blob-hole correlation model for edge turbulence and comparisons with NSTX GPI data

Abstract

Gas puff imaging (GPI) observations made in NSTX [Zweben S J, et al., 2017 Phys. Plasmas 24 102509] have revealed two-point spatial correlations of edge and scrape-off layer turbulence in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this paper, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlation patterns that are qualitatively similar to the GPI data in several respects. Effects of the reference location (confined surfaces or scrape-off layer), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored and discussed with respect to experimental observations. Additional analysis of the experimental GPI dataset is performed to further test this blob-hole correlation model. A time delay two-point spatial correlation study did not reveal inward propagation of the negative correlation structures that were postulated to correspond to holes in the data nor did it suggest that the negative correlation structures are due to neutral shadowing. However, tracing ofmore » the highest and lowest values (extrema) of the normalized GPI fluctuations shows strong evidence for mean inward propagation of minima and outward propagation of maxima, in qualitative agreement with theoretical expectations. Other properties of the experimentally observed extrema are discussed.« less

Creator(s)/Author(s):
; ;
Publication Date:
DOE Contract Number:  
AC02-09CH11466
Product Type:
Dataset
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
U. S. Department of Energy
OSTI Identifier:
1562021
DOI:
10.11578/1562021

Citation Formats

Myra, J R, Zweben, S J, and Russell, D A. Blob-hole correlation model for edge turbulence and comparisons with NSTX GPI data. United States: N. p., 2018. Web. doi:10.11578/1562021.
Myra, J R, Zweben, S J, & Russell, D A. Blob-hole correlation model for edge turbulence and comparisons with NSTX GPI data. United States. doi:10.11578/1562021.
Myra, J R, Zweben, S J, and Russell, D A. 2018. "Blob-hole correlation model for edge turbulence and comparisons with NSTX GPI data". United States. doi:10.11578/1562021. https://www.osti.gov/servlets/purl/1562021. Pub date:Sun Jul 01 00:00:00 EDT 2018
@article{osti_1562021,
title = {Blob-hole correlation model for edge turbulence and comparisons with NSTX GPI data},
author = {Myra, J R and Zweben, S J and Russell, D A},
abstractNote = {Gas puff imaging (GPI) observations made in NSTX [Zweben S J, et al., 2017 Phys. Plasmas 24 102509] have revealed two-point spatial correlations of edge and scrape-off layer turbulence in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this paper, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlation patterns that are qualitatively similar to the GPI data in several respects. Effects of the reference location (confined surfaces or scrape-off layer), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored and discussed with respect to experimental observations. Additional analysis of the experimental GPI dataset is performed to further test this blob-hole correlation model. A time delay two-point spatial correlation study did not reveal inward propagation of the negative correlation structures that were postulated to correspond to holes in the data nor did it suggest that the negative correlation structures are due to neutral shadowing. However, tracing of the highest and lowest values (extrema) of the normalized GPI fluctuations shows strong evidence for mean inward propagation of minima and outward propagation of maxima, in qualitative agreement with theoretical expectations. Other properties of the experimentally observed extrema are discussed.},
doi = {10.11578/1562021},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {7}
}

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