Reduction of inward momentum flux by damped eigenmodes

Journal Article · Tue Dec 15 04:00:00 EST 2009 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3271158· OSTI ID:21371237

Terry, P W; Baver, D A; Hatch, D R ^[1]

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1. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

The inward momentum flux driven by the off-diagonal pressure gradient in a fluid model for ion temperature gradient turbulence with large Richardson number is significantly reduced by the excitation of stable eigenmodes. This is accomplished primarily through the amplitude autocorrelation of the damped eigenmode, which, in the flux, directly counteracts the quasilinear contribution of the unstable eigenmode. Stable eigenmode cross correlations also contribute to the flux, but the symmetry of conjugate pairing of growing and damped eigenmodes leads to significant cancellations between cross correlation terms. Conjugate symmetry is a property of unstable wavenumbers but applies to the whole of the saturated state because damped eigenmodes in the unstable range prevent the spread of energy outside that range. The heat and momentum fluxes are nearly isomorphous when expressed in terms of the eigenmode correlations. Due to this similarity of form, the thermodynamic constraint, which keeps the heat flux outward even when significantly reduced by the damped eigenmode, results in a momentum flux that remains inward, even though it is also reduced by the damped eigenmode. The isomorphism is not perfect. When the contribution of stable eigenmode cross correlations to the flux do not cancel, the momentum flux can reverse sign and become outward.

• OSTI ID: 21371237
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 12 Vol. 16; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EIGENFUNCTIONS
EIGENVALUES
ENERGY TRANSFER
FUNCTIONS
HEAT FLUX
HEAT TRANSFER
PLASMA
TURBULENCE