Topological constraints on magnetic relaxation

TY - JOUR

T1 - Topological constraints on magnetic relaxation

A1 - Yeates,A. R.

A1 - Hornig,G.

A1 - Wilmot-Smith,A. L.

AU - Yeates,A. R.

AU - Hornig,G.

AU - Wilmot-Smith,A. L.

PY - 2010/8/16

Y1 - 2010/8/16

N2 - <p>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.</p>

AB - <p>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.</p>

KW - Energy principle

KW - Global invariants

KW - Fields

KW - Helicity

KW - Reconnection

KW - Plasmas

U2 - 10.1103/PhysRevLett.105.085002

DO - 10.1103/PhysRevLett.105.085002

M1 - Article

JO - Physical Review Letters

JF - Physical Review Letters

SN - 0031-9007

IS - 8

VL - 105

SP - -

ER -