Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device

T. Ido; K. Itoh; M. Osakabe; M. Lesur; A. Shimizu; K. Ogawa; K. Toi; M. Nishiura; S. Kato; M. Sasaki; K. Ida; S. Inagaki; S. I. Itoh

doi:10.1103/PhysRevLett.116.015002

Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device

T. Ido, K. Itoh, M. Osakabe, M. Lesur, A. Shimizu, K. Ogawa, K. Toi, M. Nishiura, S. Kato, M. Sasaki, K. Ida, S. Inagaki, S. I. Itoh

Division of Nuclear Fusion Dynamics

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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.

Original language	English
Article number	015002
Journal	Physical review letters
Volume	116
Issue number	1
DOIs	https://doi.org/10.1103/PhysRevLett.116.015002
Publication status	Published - Jan 8 2016

All Science Journal Classification (ASJC) codes

Physics and Astronomy(all)

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10.1103/PhysRevLett.116.015002

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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, S. I. (2016). Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device. Physical review letters, 116(1), Article 015002. https://doi.org/10.1103/PhysRevLett.116.015002

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 2016, 'Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device', Physical review letters, vol. 116, no. 1, 015002. https://doi.org/10.1103/PhysRevLett.116.015002

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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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AU - Ido, T.

AU - Itoh, K.

AU - Osakabe, M.

AU - Lesur, M.

AU - Shimizu, A.

AU - Ogawa, K.

AU - Toi, K.

AU - Nishiura, M.

AU - Kato, S.

AU - Sasaki, M.

AU - Ida, K.

AU - Inagaki, S.

AU - Itoh, S. I.

PY - 2016/1/8

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N2 - 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.

AB - 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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Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device

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