title: Experimental confirmation of self-regulating turbulence paradigm in two-dimensional spectral condensation.
abstract: Turbulent transport in magnetic fusion plasmas can be significantly suppressed by Reynolds-stress-induced zonal flows, allowing effective plasma confinement. We present experimental evidence of spatiotemporal correlation between small-scale turbulence-induced Reynolds stress and large-scale zonal flow production in the E×B driven hydrodynamic spectral condensation. We show that Reynolds stress is generated effectively by anisotropic vorticity structures possessing collective tilt angle. The maximum amplitude of the tilt, the Reynolds stress, and the mean zonal flow production coincide with the transition time of the velocity field, indicating a key role of turbulence-induced Reynolds stress in the condensation of the flow. The analysis of the energy transfer between turbulence and zonal flow shows coherent oscillations with π/2 phase delay, thus indicating a predator-prey-like interaction between zonal flow and turbulence.
authors.affiliation: University of California, Los Angeles, Los Angeles, California 90095, USA.
authors.forename: L
authors.initials: L
authors.lastname: Bardóczi
authors.affiliation: Wigner RCP, EURATOM Association, 1121 Budapest, Hungary.
authors.forename: A
authors.initials: A
authors.lastname: Bencze
authors.affiliation: Széchenyi István University, EURATOM Association, 9026 Győr, Hungary and Institute of Plasma Physics AS CR, v.v.i., 18200 Prague, Czech Republic.
authors.forename: M
authors.initials: M
authors.lastname: Berta
authors.affiliation: University of California, Los Angeles, Los Angeles, California 90095, USA.
authors.forename: L
authors.initials: L
authors.lastname: Schmitz