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On the detection of Reynolds stress as a driving and damping mechanism of geodesic acoustic modes and zonal flows

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Scott,  B.
Tokamak Theory (TOK), Max Planck Institute for Plasma Physics, Max Planck Society;

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Citation

Ramisch, M., Stroth, U., Niedner, S., & Scott, B. (2003). On the detection of Reynolds stress as a driving and damping mechanism of geodesic acoustic modes and zonal flows. New Journal of Physics, 5: 12. Retrieved from http://www.iop.org/EJ/abstract/1367-2630/5/1/312.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0027-2314-D
Abstract
Bispectral analysis has been proposed as a diagnostic for Reynolds stress (RS) as a driving mechanism of zonal flows (ZF) in toroidally confined plasmas. A turbulence simulation code was used to test this technique on a well-defined system. It turned out that the geodesic acoustic mode dominates the poloidal flow spectrum and that it reduces radial transport in the same way as does a low-frequency ZF. Using the total cross- bicoherence, a correlation between RS and large-scale poloidal flows could be detected. The experimentally more accessible auto-bicoherences did not prove to be a useful quantity for studying this interaction. RS was not observed as a precursor of the flow; rather it appears simultaneously in the region of radial flow shear.