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Title: On the dynamics of turbulent transport near marginal stability

Abstract

A general methodology for describing the dynamics of transport near marginal stability is formulated. Marginal stability is a special case of the more general phenomenon of self-organized criticality. Simple, one field models of the dynamics of tokamak plasma self-organized criticality have been constructed, and include relevant features such as sheared mean flow and transport bifurcations. In such models, slow mode (i.e. large scale, low frequency transport events) correlation times determine the behavior of transport dynamics near marginal stability. To illustrate this, impulse response scaling exponents (z) and turbulent diffusivities (D) have been calculated for the minimal (Burgers) and sheared flow models. For the minimal model, z = 1 (indicating ballastic propagation) and D {approximately}(S{sub 0}{sup 2}){sup 1/3}, where S{sub 0}{sup 2} is the noise strength. With an identically structured noise spectrum and flow with shearing rate exceeding the ambient decorrelation rate for the largest scale transport events, diffusion is recovered with z = 2 and D {approximately} (S{sub 0}{sup 2}){sup 3/5}. This indicates a qualitative change in the dynamics, as well as a reduction in losses. These results are consistent with recent findings from {rho} scaling scans. Several tokamak transport experiments are suggested.

Authors:
 [1];  [2]
+ Show Author Affiliations
  1. California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics|[General Atomics, San Diego, CA (United States)
  2. Princeton Univ., NJ (United States). Plasma Physics Lab.
Publication Date:
Research Org.:
Princeton Univ., NJ (United States). Plasma Physics Lab.
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
33136
Report Number(s):
PPPL-3053
ON: DE95008706; TRN: 95:008994
DOE Contract Number:
AC02-76CH03073; FG03-88ER53275
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Mar 1995
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; TOKAMAK DEVICES; TURBULENT FLOW; CHARGED-PARTICLE TRANSPORT; PLASMA INSTABILITY; CONFINEMENT TIME; DIFFUSION; PLASMA CONFINEMENT

Citation Formats

Diamond, P.H., and Hahm, T.S. On the dynamics of turbulent transport near marginal stability. United States: N. p., 1995. Web. doi:10.2172/33136.
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Diamond, P.H., & Hahm, T.S. On the dynamics of turbulent transport near marginal stability. United States. doi:10.2172/33136.
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Diamond, P.H., and Hahm, T.S. Wed . "On the dynamics of turbulent transport near marginal stability". United States. doi:10.2172/33136. https://www.osti.gov/servlets/purl/33136.
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@article{osti_33136,
title = {On the dynamics of turbulent transport near marginal stability},
author = {Diamond, P.H. and Hahm, T.S.},
abstractNote = {A general methodology for describing the dynamics of transport near marginal stability is formulated. Marginal stability is a special case of the more general phenomenon of self-organized criticality. Simple, one field models of the dynamics of tokamak plasma self-organized criticality have been constructed, and include relevant features such as sheared mean flow and transport bifurcations. In such models, slow mode (i.e. large scale, low frequency transport events) correlation times determine the behavior of transport dynamics near marginal stability. To illustrate this, impulse response scaling exponents (z) and turbulent diffusivities (D) have been calculated for the minimal (Burgers) and sheared flow models. For the minimal model, z = 1 (indicating ballastic propagation) and D {approximately}(S{sub 0}{sup 2}){sup 1/3}, where S{sub 0}{sup 2} is the noise strength. With an identically structured noise spectrum and flow with shearing rate exceeding the ambient decorrelation rate for the largest scale transport events, diffusion is recovered with z = 2 and D {approximately} (S{sub 0}{sup 2}){sup 3/5}. This indicates a qualitative change in the dynamics, as well as a reduction in losses. These results are consistent with recent findings from {rho} scaling scans. Several tokamak transport experiments are suggested.},
doi = {10.2172/33136},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 1995},
month = {Wed Mar 01 00:00:00 EST 1995}
}
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Technical Report:
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DOI:  10.2172/33136
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