%0 Journal Article
%T Chaos in driven Alfv¨¦n systems: unstable periodic orbits and chaotic saddles
%A A. C.-L. Chian
%A W. M. Santana
%A E. L. Rempel
%A F. A. Borotto
%A T. Hada
%A Y. Kamide
%J Nonlinear Processes in Geophysics (NPG)
%D 2007
%I Copernicus Publications
%X The chaotic dynamics of Alfv¨¦n waves in space plasmas governed by the derivative nonlinear Schr dinger equation, in the low-dimensional limit described by stationary spatial solutions, is studied. A bifurcation diagram is constructed, by varying the driver amplitude, to identify a number of nonlinear dynamical processes including saddle-node bifurcation, boundary crisis, and interior crisis. The roles played by unstable periodic orbits and chaotic saddles in these transitions are analyzed, and the conversion from a chaotic saddle to a chaotic attractor in these dynamical processes is demonstrated. In particular, the phenomenon of gap-filling in the chaotic transition from weak chaos to strong chaos via an interior crisis is investigated. A coupling unstable periodic orbit created by an explosion, within the gaps of the chaotic saddles embedded in a chaotic attractor following an interior crisis, is found numerically. The gap-filling unstable periodic orbits are responsible for coupling the banded chaotic saddle (BCS) to the surrounding chaotic saddle (SCS), leading to crisis-induced intermittency. The physical relevance of chaos for Alfv¨¦n intermittent turbulence observed in the solar wind is discussed.
%U http://www.nonlin-processes-geophys.net/14/17/2007/npg-14-17-2007.html