Chaos in Reversed-field-pinch Plasma Simulation and Experiment
Christopher Watts, D. E. Newman, and J.
C.
Sprott
Department of Physics, University
of Wisconsin--Madison, Wisconsin 53706
(Received 4 October 1993)
ABSTRACT
We investigate the possibility that chaos and simple determinism are
governing
the dynamics of reversed-field-pinch (RFP) plasmas using data from both
numerical simulations and experiment. A large repertoire of
nonlinear-analysis
techniques is used to identify low-dimensional chaos. These tools
include
phase portraits and Poincare sections, correlation dimension, the
spectrum
of Lyapunov exponents, and short-term predictability. In addition,
nonlinear-noise-reduction
techniques are applied to the experimental data in an attempt to
extract
any underlying deterministic dynamics. These are the DEBS computer
code,
which models global RFP dynamics, and the dissipative
trapped-electron-mode
model, which models drift-wave turbulence. Data from both simulations
show
strong indications of low-dimensional chaos and simple determinism.
Experimental
data were obtained from the Madison
Symmetric Torus
RFP and consist of a wide array of both global and local diagnostic
signals.
None of the signals shows any indication of low-dimensional chaos or
other
simple determinism. Moreover, most of the analysis tools indicate that
the experimental system is very high dimensional with properties
similar
to noise. Nonlinear noise reduction is unsuccessful at extracting an
underlying
deterministic system.
Ref: Christopher Watts, D. E. Newman, and J.
C.
Sprott, Physical Review E 49, 2291-2301 (1994)
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