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Title: Zonal structure effect on the nonlinear saturation of reverse shear Alfven eigenmodes

Abstract

A gyrokinetic ion/fluid electron hybrid model is used to study the nonlinear evolution of reverse shear Alfven eigenmodes (RSAE) driven by energetic particles. When only the energetic particle nonlinear effects are included, the saturation amplitude of a single-n RSAE follows the trapping scaling, δB/B∼(γ/ω)2. When the nonlinear effects of thermal ions and electrons are included, zonal structures are force generated but do not affect the saturation amplitude for γ/ω≤0.03. No spontaneous generation of zonal structures is observed, in contrast to ion-temperature-gradient-driven modes. At larger energetic particle drive, the effects of zonal structures cause a significant reduction in the RSAE saturation amplitude. The reduction is not caused by the zonal flow shearing of the RSAE, but by the force-generated n = 0 component in the thermal ion distribution function and the electron density. These n = 0 perturbations lead to nonlinear evolution of the RSAE mode structure and enhance damping.

Authors:
 [1]; ORCiD logo [1];  [1];  [1];  [1]
  1. University of Colorado at Boulder, Boulder, Colorado 80309, USA
Publication Date:
Research Org.:
Univ. of Colorado, Boulder, CO (United States); Univ. of California, Oakland, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1537272
Alternate Identifier(s):
OSTI ID: 1425244
Grant/Contract Number:  
FG02-08ER54954; AC02-05CH11231; FC02-08ER54987; FG02-08ER54987
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 3; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
Physics

Citation Formats

Chen, Y., Fu, G. Y., Collins, C., Taimourzadeh, S., and Parker, S. E. Zonal structure effect on the nonlinear saturation of reverse shear Alfven eigenmodes. United States: N. p., 2018. Web. doi:10.1063/1.5019724.
Chen, Y., Fu, G. Y., Collins, C., Taimourzadeh, S., & Parker, S. E. Zonal structure effect on the nonlinear saturation of reverse shear Alfven eigenmodes. United States. doi:10.1063/1.5019724.
Chen, Y., Fu, G. Y., Collins, C., Taimourzadeh, S., and Parker, S. E. Thu . "Zonal structure effect on the nonlinear saturation of reverse shear Alfven eigenmodes". United States. doi:10.1063/1.5019724. https://www.osti.gov/servlets/purl/1537272.
@article{osti_1537272,
title = {Zonal structure effect on the nonlinear saturation of reverse shear Alfven eigenmodes},
author = {Chen, Y. and Fu, G. Y. and Collins, C. and Taimourzadeh, S. and Parker, S. E.},
abstractNote = {A gyrokinetic ion/fluid electron hybrid model is used to study the nonlinear evolution of reverse shear Alfven eigenmodes (RSAE) driven by energetic particles. When only the energetic particle nonlinear effects are included, the saturation amplitude of a single-n RSAE follows the trapping scaling, δB/B∼(γ/ω)2. When the nonlinear effects of thermal ions and electrons are included, zonal structures are force generated but do not affect the saturation amplitude for γ/ω≤0.03. No spontaneous generation of zonal structures is observed, in contrast to ion-temperature-gradient-driven modes. At larger energetic particle drive, the effects of zonal structures cause a significant reduction in the RSAE saturation amplitude. The reduction is not caused by the zonal flow shearing of the RSAE, but by the force-generated n = 0 component in the thermal ion distribution function and the electron density. These n = 0 perturbations lead to nonlinear evolution of the RSAE mode structure and enhance damping.},
doi = {10.1063/1.5019724},
journal = {Physics of Plasmas},
number = 3,
volume = 25,
place = {United States},
year = {2018},
month = {3}
}

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