%0 Journal Article
%T Effective transport barriers in nontwist systems
%A J. D. Szezech Jr
%A I. L. Caldas
%A S. R. Lopes
%A P. J. Morrison
%A R. L. Viana
%J Physics
%D 2012
%I arXiv
%R 10.1103/PhysRevE.86.036206
%X In fluids and plasmas with zonal flow reversed shear, a peculiar kind of transport barrier appears in the shearless region, one that is associated with a proper route of transition to chaos. Using a symplectic nontwist maps, which model such zonal flows, we investigate these barriers. In particular, the standard nontwist map, a paradigm of nontwist systems, is used to analyze the parameter dependence of the transport through a broken shearless barrier. Varying a proper control parameter, we identify the onset of structures with high stickiness that give rise to an effective barrier near the broken shearless curve. Several diagnostics are used: stickiness is measured by escape time and transmissivity plots, while barriers that separate different regions of stickiness are identified by employing two indicators in the phase space, the finite-time rotation number and the finite-time Lyapunov exponent.
%U http://arxiv.org/abs/1201.3549v1