Effective transport barriers in nontwist systems

J. D. Szezech, Jr., I. L. Caldas, S. R. Lopes, P. J. Morrison, and R. L. Viana
Phys. Rev. E 86, 036206 – Published 7 September 2012

Abstract

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. These barriers have been identified in symplectic nontwist maps that model such zonal flows. We use the so-called standard nontwist map, a paradigmatic example of nontwist systems, to analyze the parameter dependence of the transport through a broken shearless barrier. On 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. Moreover, we show how these stickiness structures, and the concomitant transport reduction in the shearless region, are determined by a homoclinic tangle of the remaining dominant twin island chains. We use the finite-time rotation number, a recently proposed diagnostic, to identify transport barriers that separate different regions of stickiness. The identified barriers are comparable to those obtained by using finite-time Lyapunov exponents.

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  • Received 17 January 2012

DOI:https://doi.org/10.1103/PhysRevE.86.036206

©2012 American Physical Society

Authors & Affiliations

J. D. Szezech, Jr.1, I. L. Caldas1, S. R. Lopes2, P. J. Morrison3, and R. L. Viana2,*

  • 1Instituto de Física, Universidade de São Paulo, 5315-970, São Paulo, São Paulo, Brazil
  • 2Departamento de Física, Universidade Federal do Paraná, 81531-990, Curitiba, Paraná, Brazil
  • 3Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA

  • *Corresponding author: viana@fisica.ufpr.br

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Vol. 86, Iss. 3 — September 2012

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