Geodesic acoustic modes with poloidal mode couplings ad infinitum

2015/12/18 by Ö. D. Gürcan, Singh, Rameswar, X. Garbet +10
Earth and Planetary Sciences · #Underwater Acoustics Research #Tropical and Extratropical Cyclones Research #Seismic Waves and Analysis

paper · pdf · doi:10.48550/arxiv.1512.06066

Abstract

Geodesic acoustic modes (GAMs) are studied, for the first time, including all poloidal mode (m) couplings using drift reduced fluid equations. The nearest neighbor coupling pattern, due to geodesic curvature, leads to a semi-infinite chain model of the GAM with the mode-mode coupling matrix elements proportional to the radial wave number k_r. The infinite chain can be reduced to a renormalized bi-nodal chain with a matrix continued fractions. Convergence study of linear GAM dispersion with respect to k_r and the m-spectra confirms that high m couplings become increasingly important with k_r. The radially sorted roots overlap with experimentally measured GAM frequency profile in low collisionality shots in Tore Supra thus explaining the reduced frequency of GAM in Tore Supra.

Related

• Effects of Circulating Energetic Ions on Geodesic Acoustic Modes with Finite Wave Numbers
• Effects of the Second Harmonic and Plasma Shaping on the Geodesic Acoustic Mode
• Drift effects on electromagnetic geodesic acoustic modes
• Collisionless damping of geodesic acoustic modes
• The theoretical study on intermittency and propagation of geodesic acoustic mode in L- mode discharge near tokamak edge