Non-linear saturation mechanism of electron temperature gradient modes

The electron temperature gradient (ETG) mode is a very plausible candidate to explain the large electron particle transport and thermal conduction. Production and identification of slab ETG modes and measurement electron transport have been already reported [X. Wei, V. Sokolov, and A. K. Sen, Phys....

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Bibliographic Details
Published in:Physics of plasmas 2012-10, Vol.19 (10)
Main Authors: Tokluoglu, E. K., Sokolov, V., Sen, A. K.
Format: Article
Language:English
Subjects:
CHARGED-PARTICLE TRANSPORT
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COUPLING
DAMPING
ELECTRON TEMPERATURE
Harmonics
ION ACOUSTIC WAVES
Joining
KHZ RANGE
Mathematical models
MHZ RANGE
NONLINEAR PROBLEMS
Nonlinearity
Plasmas
SATURATION
TEMPERATURE GRADIENTS
TEMPERATURE MEASUREMENT
THERMAL CONDUCTION
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Summary:The electron temperature gradient (ETG) mode is a very plausible candidate to explain the large electron particle transport and thermal conduction. Production and identification of slab ETG modes and measurement electron transport have been already reported [X. Wei, V. Sokolov, and A. K. Sen, Phys. Plasmas 17, 042108 (2010); V. Sokolov and A. K. Sen, Phys. Rev. Lett. (2011)]. Now, we develop a theoretical model of non-linear saturation mechanism of ETG mode based on the three wave coupling of an unstable high frequency ETG mode with a damped ETG radial harmonic and a damped ion acoustic (IA) mode. Bicoherence analysis of Columbia linear machine (CLM) data show coupling between ETG modes (∼2.4 MHz) and a low frequency mode (∼50 kHz). The large damping drive of the ETG radial harmonic accompanied by the smaller but finite damping of the IA mode presents an energy sink for the unstable ETG mode, thus causing saturation. This model predicts a saturation level of ∼10% and agrees with the observed levels of ETG modes in the CLM.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.4759009