Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

Journal Article · Fri Apr 15 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4946869· OSTI ID:22599129

Castillo-Negrete, Diego del; Blazevski, Daniel ^[1]

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1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)

Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in three-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in large helical device and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude of modulated heat pulses.

• OSTI ID: 22599129
• Journal Information: Physics of Plasmas, Vol. 23, Issue 4; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CHAOS THEORY
COMPUTERIZED SIMULATION
DOUBLET-3 DEVICE
FOURIER TRANSFORMATION
GREEN FUNCTION
HEAT
HEAT TRANSFER
LAGRANGIAN FUNCTION
LHD DEVICE
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETIC ISLANDS
MAGNETIC SURFACES
NUMERICAL SOLUTION
PULSES
STOCHASTIC PROCESSES
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE
TRANSPORT THEORY