Volume 83, Number 3, August 2008
|Number of page(s)||6|
|Section||Physics of Gases, Plasmas and Electric Discharges|
|Published online||01 July 2008|
Radial structures and nonlinear excitation of geodesic acoustic modes
Associazione Euratom-ENEA sulla Fusione, C.R. Frascati - C.P. 65, 00044 Frascati, Italy, EU
2 Department of Physics and Astronomy, University of California - Irvine, CA 92697-4575, USA
3 Institute for Fusion Theory and Simulation, Zhejiang University - Hangzhou 310027, PRC
Corresponding author: email@example.com
Accepted: 16 June 2008
Geodesic acoustic modes (GAM) are shown to constitute a continuous spectrum due to radial inhomogeneities. The importance and theoretical as well as experimental implications of this fact are discussed in this work. The existence of a singular layer causes GAM to mode convert to short-wavelength kinetic GAM (KGAM) via finite ion Larmor radii; analogous to kinetic Alfvén waves (KAW). Furthermore, it is shown that KGAM can be nonlinearly excited by drift-wave (DW) turbulence via 3-wave parametric interactions, and the resultant driven-dissipative nonlinear system exhibits typical prey-predator self-regulatory dynamics, consistent with recent experimental observations on HL-2A. The degeneracy of GAM/KGAM with beta-induced Alfvén eigenmodes (BAE) is demonstrated and discussed, with emphasis on its important role in the complex self-organized behaviors of burning plasmas.
PACS: 52.35.Fp – Electrostatic waves and oscillations (e.g., ion-acoustic waves) / 52.35.Mw – Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.) / 52.35.Lv – Other linear waves
© EPLA, 2008
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