(TH/P2-1) Nonlinear equilibria, stability and generation of zonal structures in toroidal plasmas

L. Chen1), F. Zonca2)
1) Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697-4575, United States of America
2) Associazione Euratom-ENEA sulla Fusione, C.P. 65 - I-00044 - Frascati, Rome, Italy

Abstract.  The long-lived saturated zonal flow (ZF) structures, spontaneously generated by drift-wave (DW) turbulence, are viewed as generators of nonlinear equilibria. Here, we derive a nonlinear evolution equation for the zonal response, valid for arbitrary wavelengths, which gives the temporal evolution of the zonal structures, whose time-asymptotic behavior corresponds to the nonlinear equilibrium. Its corresponding stability, meanwhile, determines the nature of the ZF instability and the nonlinear up-shift of turbulent transport thresholds. On a shorter-time scale, the temporal evolution of the zonal response describes the DW-ZF generation and the regulation of the DW intensity by the ZFs. As application, we present a kinetic stability analysis of zonal structures in the ITG case and estimate the nonlinear up-shift of the threshold for ITG driven turbulent transport. * This work is supported by U.S. D.o.E.

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