Observation of coherent bicoherence and biphase in potential fluctuations around geodesic acoustic mode frequency on JFT-2M

Y. Nagashima, K. Itoh, S. I. Itoh, K. Hoshino, A. Fujisawa, A. Ejiri, Y. Takase, M. Yagi, K. Shinohara, K. Uehara, Y. Kusama

研究成果: Contribution to journalArticle査読

24 被引用数 (Scopus)

抄録

Two types of small-poloidal wavelength low frequency floating potential fluctuations (∼1 kHz, and 10-15 kHz) are observed in the edge region of ohmically heated plasmas in the JFT-2M tokamak. The higher frequency fluctuations are inferred as geodesic acoustic modes (GAMs). Significant bicoherences between both modes and the broad-band fluctuations are observed simultaneously; however, frequency ranges are different. A significant bicoherence range is from 70 to 125 kHz at the lower frequency modes (LFM) and is from 20 to 125 kHz at the GAM. Phase angles at the significant bicoherences are coherent around π. These results indicate that both modes are nonlinearly coupled to the broad-band fluctuations. Two spectral peaks are observed around the GAM frequency and the difference in peak frequencies is around the LFM frequency, suggesting nonlinear couplings between the LFM and the GAM. However, the modulation of the GAM by the LFM is not conclusive. In this paper, the results of the letter (Nagashima et al 2005 Phys. Rev. Lett. 95 095002) are presented in detail.

本文言語英語
ページ(範囲)A377-A386
ジャーナルPlasma Physics and Controlled Fusion
48
5 A
DOI
出版ステータス出版済み - 5 2006

All Science Journal Classification (ASJC) codes

  • 原子力エネルギーおよび原子力工学
  • 凝縮系物理学

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