title: Observation of nonlinear coupling between small-poloidal wave-number potential fluctuations and turbulent potential fluctuations in Ohmically heated plasmas in the JFT-2M tokamak.
abstract: Two types of electrostatic modes with small-poloidal wave numbers (approximately 1 and 10-15 kHz) are observed in the edge region of Ohmically heated plasmas in the JFT-2M tokamak. The envelope of the higher frequency coherent mode is modulated at the frequency of the lower frequency mode. A bispectral analysis revealed that a significant nonlinear coupling among the two types of fluctuations and the broadband background turbulent potential fluctuations occurs inside the last closed magnetic flux surface, suggesting that a nonlinear process such as the parametric-modulational instability is involved.
authors.affiliation: University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nagashima
authors.forename: K
authors.initials: K
authors.lastname: Hoshino
authors.forename: A
authors.initials: A
authors.lastname: Ejiri
authors.forename: K
authors.initials: K
authors.lastname: Shinohara
authors.forename: Y
authors.initials: Y
authors.lastname: Takase
authors.forename: K
authors.initials: K
authors.lastname: Tsuzuki
authors.forename: K
authors.initials: K
authors.lastname: Uehara
authors.forename: H
authors.initials: H
authors.lastname: Kawashima
authors.forename: H
authors.initials: H
authors.lastname: Ogawa
authors.forename: T
authors.initials: T
authors.lastname: Ido
authors.forename: Y
authors.initials: Y
authors.lastname: Kusama
authors.forename: Y
authors.initials: Y
authors.lastname: Miura