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Wang H, Todo Y, Ido T, Suzuki Y. Chirping and Sudden Excitation of Energetic-Particle-Driven Geodesic Acoustic Modes in a Large Helical Device Experiment. PHYSICAL REVIEW LETTERS 2018; 120:175001. [PMID: 29756817 DOI: 10.1103/physrevlett.120.175001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 01/24/2018] [Indexed: 06/08/2023]
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.
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Affiliation(s)
- Hao Wang
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - Yasushi Todo
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292, Japan
| | - Takeshi Ido
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - Yasuhiro Suzuki
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292, Japan
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Ido T, Itoh K, Osakabe M, Lesur M, Shimizu A, Ogawa K, Toi K, Nishiura M, Kato S, Sasaki M, Ida K, Inagaki S, Itoh SI. Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device. PHYSICAL REVIEW LETTERS 2016; 116:015002. [PMID: 26799023 DOI: 10.1103/physrevlett.116.015002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Indexed: 06/05/2023]
Abstract
Abrupt and strong excitation of a mode has been observed when the frequency of a chirping energetic-particle driven geodesic acoustic mode (EGAM) reaches twice the geodesic acoustic mode (GAM) frequency. The frequency of the secondary mode is the GAM frequency, which is a half-frequency of the primary EGAM. Based on the analysis of spatial structures, the secondary mode is identified as a GAM. The phase relation between the secondary mode and the primary EGAM is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. The results suggest that the primary mode (EGAM) contributes to nonlinear destabilization of a subcritical mode.
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Affiliation(s)
- T Ido
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - K Itoh
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - M Osakabe
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Study), 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - M Lesur
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
| | - A Shimizu
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - K Ogawa
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Study), 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - K Toi
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - M Nishiura
- Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanohara, Kashiwa, Chiba 277-8561, Japan
| | - S Kato
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - M Sasaki
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
| | - K Ida
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Study), 322-6 Oroshi, Toki, Gifu 509-5292, Japan
| | - S Inagaki
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
| | - S-I Itoh
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
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