Significant effect of plasma compressibility on nonlinear mode coupling of Alfvén eigenmodes

M. Hirota, N. Aiba

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Nonlinear mode coupling of the (shear) Alfvén eigenmodes (AEs) is studied both analytically and numerically to understand the effect of the magnetohydrodynamic nonlinearity on the saturation mechanism. The energy transfer via the mode coupling can restrict the amplitude to a level that is estimated by the frequency mismatch and the coupling coefficient among the coupled modes. For the cases of cylindrical and toroidal geometries, new numerical codes are developed to calculate the coupling coefficient directly according to the Lagrangian theory of weakly nonlinear perturbations. It is shown that the shear AEs can couple with each other through the small compressional components of their eigenfunctions. By assuming low-β plasma, an analytic estimation of the coupling coefficient (∝ √β) is derived in the cylindrical case. A coupling of reversed shear AEs in toroidal geometry indicates a more effective energy transfer at a lower amplitude level owing to the enhanced compressional perturbations in the poloidal sidebands.

Original languageEnglish
Article number073037
JournalNuclear Fusion
Volume51
Issue number7
DOIs
Publication statusPublished - 2011 Jul
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Fingerprint Dive into the research topics of 'Significant effect of plasma compressibility on nonlinear mode coupling of Alfvén eigenmodes'. Together they form a unique fingerprint.

Cite this