53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011;
Salt Lake City, Utah
Session JI2: 3D Equilibrium, Stability and Control
2:00 PM–5:00 PM,
Tuesday, November 15, 2011
Room: Ballroom BD
Chair: Mike Mauel, Columbia University
Abstract ID: BAPS.2011.DPP.JI2.3
Abstract: JI2.00003 : Local and Nonlocal Parallel Heat Transport in General Magnetic Fields*
3:00 PM–3:30 PM
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Abstract
Author:
Diego del-Castillo-Negrete
(Oak Ridge National Laboratory)
Transport in magnetized plasmas is a topic of fundamental
interest in controlled fusion, space plasmas, and astrophysics.
Three issues make this problem particularly challenging: (i) The
{\em extreme anisotropy} between the parallel (i.e., along the
magnetic field), $\chi_\parallel$, and the perpendicular,
$\chi_\perp$, conductivities; (ii) Magnetic {\em field lines
chaos} which may preclude the use of magnetic coordinates;
and (iii) {\em Nonlocal parallel transport} in the limit of small
collisionality. As a result of these challenges, standard
finite-difference and finite-element numerical methods face
significant limitations. Motivated by the strong anisotropy
typically encountered in magnetized plasmas ($\chi_\perp
/\chi_\parallel $ may be less than $10^{-10}$ in fusion plasmas)
we consider heat transport in the extreme anisotropic regime,
$\chi_\perp=0$. To overcome the limitations of previous
approaches, we present a novel Lagrangian Green's function method
that bypasses the need to discretize and invert the transport
operators on a grid.\footnote{D. del-Castillo-Negrete and L.
Chacon, Phys. Rev. Lett. {\bf 106} 195004 (2011).} The method
allows the integration of the parallel transport equation without
perpendicular pollution, preserving the positivity of the
temperature field at all times. The method is applicable to local
(i.e., diffusive) and non-local (e.g., free streaming) heat flux
closures in integrable or chaotic magnetic fields. The method is
applied to study: (i) Local and non-local parallel temperature
mixing and flattening inside magnetic islands; (ii) Fractal
structure of the Devil's staircase temperature profile in the
previously inaccessible $\chi_\perp=0$ regime in weakly chaotic
fields; (iii) Transport in fully chaotic fields. For the last
problem it is shown that, for local and non-local parallel
closures, transport is incompatible with the quasilinear
diffusion model. In particular, flux-gradient plots show clear
evidence of non-diffusive, non-local effective radial transport.
*Supported by U.S. DOE Contract DE-AC05-00OR22725.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.DPP.JI2.3