Observation of nonlinear coupling between small-poloidal wave-number potential fluctuations and turbulent potential fluctuations in Ohmically heated plasmas in the JFT-2M tokamak.
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.
Nagashima
Y
Y
University of Tokyo, Tokyo 113-0033, Japan.
Hoshino
K
K
Ejiri
A
A
Shinohara
K
K
Takase
Y
Y
Tsuzuki
K
K
Uehara
K
K
Kawashima
H
H
Ogawa
H
H
Ido
T
T
Kusama
Y
Y
Miura
Y
Y