Bispectral analysis applied to coherent floating potential fluctuations obtained in the edge plasmas on JFT-2M

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

Research output: Contribution to journalArticle

39 Citations (Scopus)


This paper presents results of bispectral analysis applied to floating potential fluctuations in the edge region of ohmically heated plasmas in the JAERI Fusion Torus-2 Modified (JFT-2M) tokamak. Inside the outermost surface of plasmas, coherent mode fluctuations (CMs) in floating potential were observed around the frequency of the geodesic acoustic mode. The squared bicoherence shows significant nonlinear couplings between the CMs and background fluctuations. The biphase at the frequency of the CMs is localized around π, while that at frequencies of background fluctuations distributes in a wide range. The total bicoherence at the frequency of the CMs is proportional to the squared amplitude of the CMs. These observations are consistent with the theoretical prediction on the drift wave-zonal flow systems. Interpretation of the absolute value of the total bicoherence is also discussed.

Original languageEnglish
Pages (from-to)S1-S15
JournalPlasma Physics and Controlled Fusion
Issue number4
Publication statusPublished - Apr 1 2006


All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

Cite this