Chirping and Sudden Excitation of Energetic-Particle-Driven Geodesic Acoustic Modes in a Large Helical Device Experiment

Physical Review Letters
Hao WangYasuhiro Suzuki

Abstract

Energetic-particle-driven geodesic acoustic modes (EGAMs) observed in a Large Helical Device experiment are investigated using a hybrid simulation code for energetic particles interacting with a magnetohydrodynamic (MHD) fluid. The frequency chirping of the primary mode and the sudden excitation of the half-frequency secondary mode are reproduced for the first time with the hybrid simulation using the realistic physical condition and the three-dimensional equilibrium. Both EGAMs have global spatial profiles which are consistent with the experimental measurements. For the secondary mode, the bulk pressure perturbation and the energetic particle pressure perturbation cancel each other out, and thus the frequency is lower than the primary mode. It is found that the excitation of the secondary mode does not depend on the nonlinear MHD coupling. The secondary mode is excited by energetic particles that satisfy the linear and nonlinear resonance conditions, respectively, for the primary and secondary modes.

References

Nov 13, 2008·Physical Review Letters·R NazikianM A Van Zeeland
Nov 13, 2008·Physical Review Letters·G Y Fu
Jan 15, 2011·Physical Review Letters·K ToiUNKNOWN LHD Experiment Group
Aug 7, 2012·Physical Review Letters·G J KramerM A Van Zeeland
Mar 22, 2013·Physical Review Letters·D ZarzosoO Thomine
Jan 23, 2016·Physical Review Letters·M LesurUNKNOWN LHD Experiment Group

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