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TJ-II:Confinement transitions: Difference between revisions
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While this phenomenon is still not completely understood, much progress has been made in recent years. It is believed that turbulent fluctuations drive sheared or zonal flows via the Reynolds Stress Mechanism. This flow then shears the turbulent eddies apart, leading to local turbulence suppression at specific radial locations, and a concomitant local reduction of transport. | While this phenomenon is still not completely understood, much progress has been made in recent years. It is believed that turbulent fluctuations drive sheared or zonal flows via the Reynolds Stress Mechanism. This mechanism transfers energy of high-frequency drift type turbulence to low wavelength modes. The zonal flow itself is radially localized and has a very long (infinite) toroidal and poloidal wavelength. This flow then shears the turbulent eddies apart, leading to local turbulence suppression at specific radial locations, and a concomitant local reduction of transport. | ||
<ref>[http://dx.doi.org/10.1088/0741-3335/47/5/R01 P.H. Diamond et al, ''Zonal flows in plasma - a review'', Plasma Phys. Control. Fusion '''47''' (2005) R35-R161]</ref> | |||
At [[TJ-II]], much effort has been invested in the experimental measurement and theoretical understanding of this phenomenon. | At [[TJ-II]], much effort has been invested in the experimental measurement and theoretical understanding of this phenomenon. | ||