Letter abstract
Nature Physics 4, 721 - 725 (2008)
Published online: 27 July 2008 | doi:10.1038/nphys1029
Anatomy of plasma turbulence
Takuma Yamada1, Sanae-I. Itoh1, Takashi Maruta2, Naohiro Kasuya3, Yoshihiko Nagashima1, Shunjiro Shinohara2, Kenichiro Terasaka2, Masatoshi Yagi1, Shigeru Inagaki1, Yoshinobu Kawai1, Akihide Fujisawa3 & Kimitaka Itoh3
Turbulence is a state of fluids and plasma where nonlinear interactions including cascades to finer scales take place to generate chaotic structure and dynamics1. However, turbulence could generate global structures2, such as dynamo magnetic field, zonal flows3, transport barriers, enhanced transport and quenching transport. Therefore, in turbulence, multiscale phenomena coevolve in space and time, and the character of plasma turbulence has been investigated in the laboratory4, 5, 6, 7, 8, 9, 10 as a modern and historical scientific mystery. Here, we report anatomical features of the plasma turbulence in the wavenumber–frequency domain by using nonlinear spectral analysis including the bi-spectrum11. First, the formation of the plasma turbulence can be regarded as a result of nonlinear interaction of a small number of irreducible parent modes that satisfy the linear dispersion relation. Second, the highlighted finding here, is the first identification of a streamer (state of bunching of drift waves12, 13) that should degrade the quality of plasmas for magnetic confinement fusion14, 15. The streamer is a poloidally localized, radially elongated global structure that lives longer than the characteristic turbulence correlation time, and our results reveal that the streamer is produced as the result of the nonlinear condensation, or nonlinear phase locking of the major triplet modes.
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
- National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
Correspondence to: Takuma Yamada1 e-mail: takuma@riam.kyushu-u.ac.jp
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