Role of secondary long wavelength structures in the saturation of electron temperature gradient driven turbulence

Journal Article · Sat Nov 15 04:00:00 EST 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3012567· OSTI ID:21259665

Jiquan, Li ^[1]; Kishimoto, Y ^[1]

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1. Department of Fundamental Energy, Kyoto University, 611-0011 Gokasho, Uji (Japan)

The dynamics of secondary long wavelength structures (LWSs) in electron temperature gradient (ETG) driven turbulence are investigated by performing gyrofluid simulations and modeling analyses in a slab geometry with an emphasis of the underlying nonlinear interaction processes. It is shown that the back-reaction of the secondary LWS on the ambient fluctuations essentially contributes to saturating ETG instability and limiting the electron transport. The LWS is nonlinearly generated mainly through the beating of the most unstable ETG modes, even a weak modulation instability. The back-reaction is identified as the enhanced stabilization of the ETG modes due to the streamer-type feature of the LWS, which dominantly produces a local poloidal mode coupling among unstable and highly damped spectral components to form a global mode, besides the suppression effect of the LWS due to the radial shearing decorrelation and/or the radial mode coupling. Finally, the correspondence between the LWS in the slab model and the quasimode observed in toroidal ETG simulation [Z. Lin et al., Phys. Plasmas 12, 056125 (2005)] and the importance of the nonlinear mode coupling in the multiscale turbulence interaction are discussed.

• OSTI ID: 21259665
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 11 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COUPLING
ELECTRON TEMPERATURE
FLUCTUATIONS
NONLINEAR PROBLEMS
PLASMA
PLASMA INSTABILITY
PLASMA SIMULATION
TEMPERATURE GRADIENTS
TURBULENCE
WAVELENGTHS