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

Hao Wang, Yasushi Todo, Takeshi Ido, Yasuhiro Suzuki

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

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.

Original languageEnglish
Article number175001
JournalPhysical review letters
Volume120
Issue number17
DOIs
Publication statusPublished - Apr 27 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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