Topological constraints on magnetic relaxation

The final state of turbulent magnetic relaxation in a reversed field pinch is well explained by Taylor's hypothesis. However, recent resistive-magnetohydrodynamic simulations of the relaxation of braided solar coronal loops have led to relaxed fields far from the Taylor state, despite the conse...

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Bibliographic Details
Published in:Physical review letters 2010-08, Vol.105 (8), p.085002-085002, Article 085002
Main Authors: Yeates, A R, Hornig, G, Wilmot-Smith, A L
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CLOSED PLASMA DEVICES
COMPUTERIZED SIMULATION
HELICITY
MAGNETIC FIELDS
MAPPING
MATHEMATICS
PARTICLE PROPERTIES
PINCH DEVICES
PINCH EFFECT
PLASMA SIMULATION
RELAXATION
REVERSE-FIELD PINCH
REVERSED-FIELD PINCH DEVICES
SIMULATION
THERMONUCLEAR DEVICES
TOPOLOGY
TOROIDAL PINCH DEVICES
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Summary:The final state of turbulent magnetic relaxation in a reversed field pinch is well explained by Taylor's hypothesis. However, recent resistive-magnetohydrodynamic simulations of the relaxation of braided solar coronal loops have led to relaxed fields far from the Taylor state, despite the conservation of helicity. We point out the existence of an additional topological invariant in any flux tube with a nonzero field: the topological degree of the field line mapping. We conjecture that this constrains the relaxation, explaining why only one of three example simulations reaches the Taylor state.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.105.085002