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Title: Dissipation in the magnetic turbulence of reversed field pinch plasmas

Abstract

Reversed field pinch (RFP) plasmas are subject to tearing instability that creates a broad spectrum of magnetic fluctuations. The dominant fluctuations have poloidal and toroidal mode numbers (m,n)=(1,6−10) and can grow to 2–3% of the mean magnetic field. Through nonlinear coupling, this growth culminates in a strong reconnection event and broadening of the magnetic spectrum extending to the ion gyroradius scale. Multiple developments occur during the reconnection stage: ions and electrons are energized, magnetic fluctuation amplitudes increase, plasma flow is halted, and the toroidal magnetic flux increases in a sawtooth-like fashion as the RFP dynamo becomes stronger. Magnetic fluctuations are measured in the plasma edge at multiple radial locations from r/a = 0.75 to 0.96 to assess and characterize the magnetic turbulence. The measured spectrum perpendicular to the mean field, S(k⊥), can be fit to a model spectrum consisting of power-law and exponential component with one free parameter that characterizes dissipation. The measured dissipation is much larger than estimated from classical viscous or resistive dissipation, but it is consistent with a flow damping measurement of anomalous viscosity. The measurements show an evolution of the spectrum during which fluctuation power builds up in the smallest wavenumbers and cascades to the larger wavenumber duemore » to the nonlinear coupling between the linear (m, n) = (1, > 6) and the nonlinear (m, n) = (0, 1) tearing modes.« less

Authors:
ORCiD logo [1];  [2];  [2]; ORCiD logo [2]; ORCiD logo [3];  [3]
  1. Florida A & M University, Tallahassee, FL (United States); TAE Technologies, Inc., Foothill Ranch, CA (United States)
  2. Univ. of Wisconsin, Madison, WI (United States)
  3. Florida A & M University, Tallahassee, FL (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States); Florida A & M University, Tallahassee, FL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1849042
Alternate Identifier(s):
OSTI ID: 1797339
Grant/Contract Number:  
FC02-05ER54814; FG02-85ER53212; FG02-97ER54417; SC0018266
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 28; Journal Issue: 6; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Physics; Plasma confinement; Plasma waves; Plasma heating; Plasma flows; Cyclotron resonance; Magnetic energy; Magnetic reconnection; Plasma instabilities; Spectrograms

Citation Formats

Titus, J. B., Almagri, A. F., Terry, P. W., Sarff, J. S., Mezonlin, E. D., and Johnson, J. A. Dissipation in the magnetic turbulence of reversed field pinch plasmas. United States: N. p., 2021. Web. doi:10.1063/5.0044808.
Titus, J. B., Almagri, A. F., Terry, P. W., Sarff, J. S., Mezonlin, E. D., & Johnson, J. A. Dissipation in the magnetic turbulence of reversed field pinch plasmas. United States. https://doi.org/10.1063/5.0044808
Titus, J. B., Almagri, A. F., Terry, P. W., Sarff, J. S., Mezonlin, E. D., and Johnson, J. A. Wed . "Dissipation in the magnetic turbulence of reversed field pinch plasmas". United States. https://doi.org/10.1063/5.0044808. https://www.osti.gov/servlets/purl/1849042.
@article{osti_1849042,
title = {Dissipation in the magnetic turbulence of reversed field pinch plasmas},
author = {Titus, J. B. and Almagri, A. F. and Terry, P. W. and Sarff, J. S. and Mezonlin, E. D. and Johnson, J. A.},
abstractNote = {Reversed field pinch (RFP) plasmas are subject to tearing instability that creates a broad spectrum of magnetic fluctuations. The dominant fluctuations have poloidal and toroidal mode numbers (m,n)=(1,6−10) and can grow to 2–3% of the mean magnetic field. Through nonlinear coupling, this growth culminates in a strong reconnection event and broadening of the magnetic spectrum extending to the ion gyroradius scale. Multiple developments occur during the reconnection stage: ions and electrons are energized, magnetic fluctuation amplitudes increase, plasma flow is halted, and the toroidal magnetic flux increases in a sawtooth-like fashion as the RFP dynamo becomes stronger. Magnetic fluctuations are measured in the plasma edge at multiple radial locations from r/a = 0.75 to 0.96 to assess and characterize the magnetic turbulence. The measured spectrum perpendicular to the mean field, S(k⊥), can be fit to a model spectrum consisting of power-law and exponential component with one free parameter that characterizes dissipation. The measured dissipation is much larger than estimated from classical viscous or resistive dissipation, but it is consistent with a flow damping measurement of anomalous viscosity. The measurements show an evolution of the spectrum during which fluctuation power builds up in the smallest wavenumbers and cascades to the larger wavenumber due to the nonlinear coupling between the linear (m, n) = (1, > 6) and the nonlinear (m, n) = (0, 1) tearing modes.},
doi = {10.1063/5.0044808},
journal = {Physics of Plasmas},
number = 6,
volume = 28,
place = {United States},
year = {Wed Jun 16 00:00:00 EDT 2021},
month = {Wed Jun 16 00:00:00 EDT 2021}
}

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