Zonal flows induced by symmetry breaking with existence of geodesic acoustic modes

Makoto Sasaki, K. Itoh, Sanae Itoh, Naohiro Kasuya

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The nonlinear dynamics of zonal flows (ZFs) is investigated when geodesic acoustic modes (GAMs) have substantial influence on plasma states. Simultaneous existence of multiple GAMs with different radial phase velocities gives additional nonlinear mode couplings, and asymmetry of the turbulence spectrum induces energy exchanges between GAMs and a ZF. A set of model equations is derived to describe the nonlinear dynamics of a ZF, GAMs and ambient turbulence. The model includes the mechanism of ZF generation by a pair of GAMs, and the back interaction from the turbulence is solved self-consistently. Two stationary solutions are obtained; one is the known solution that the GAM propagates as a travelling wave with no ZF excitation, and the other is a new solution that a pair of GAMs forms a standing wave, which induces a ZF. The accessibility to the steady states, and the threshold for the transition between them are obtained. The GAM and ZF formation in the new state affects the background plasmas. The effects on the turbulent heat diffusivity and the ion heating rate are discussed.

Original languageEnglish
Article number023009
JournalNuclear Fusion
Volume52
Issue number2
DOIs
Publication statusPublished - Feb 1 2012

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broken symmetry
acoustics
turbulence
phase velocity
standing waves
traveling waves
radial velocity
coupled modes
diffusivity
energy transfer
asymmetry
heat
heating
thresholds
excitation
ions
interactions

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Zonal flows induced by symmetry breaking with existence of geodesic acoustic modes. / Sasaki, Makoto; Itoh, K.; Itoh, Sanae; Kasuya, Naohiro.

In: Nuclear Fusion, Vol. 52, No. 2, 023009, 01.02.2012.

Research output: Contribution to journalArticle

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