Conditions for the fast reconnection mechanism in three dimensions

Journal Article · Thu Sep 15 04:00:00 EDT 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2047327· OSTI ID:20764528

Ugai, M; Zheng, L ^[1]

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1. Department of Computer Science, Faculty of Engineering, Ehime University, Matsuyama 790-8577 (Japan)

Physical conditions for the fast reconnection mechanism to be realized as an eventual solution of magnetohydrodynamic equations are examined by three-dimensional (3D) simulations for different resistivity models. Initiated by a small disturbance in a current sheet, all the phenomena grow by the self-consistent interaction between the 3D reconnection flow and the effective resistivity. For the classical resistivity {eta} due to Coulomb collisions, where {eta}{proportional_to}T{sup -3/2}, no effective reconnection occurs, since the resistivity becomes reduced with the increase in temperature T as magnetic reconnection proceeds, which indicates the negative feedback between the reconnection flow and the resistivity. For the anomalous resistivity, where {eta} increases with the current density when a threshold is exceeded, the positive feedback eventually leads to the fast reconnection mechanism as a nonlinear instability. In this case, the resistivity is distinctly enhanced at the slow shock layer attached to the diffusion region, so that the shock layer becomes thicker, and resistive tearing is more likely to take place in the diffusion region. For the anomalous resistivity, where {eta} increases with the relative electron-ion drift velocity when a threshold is exceeded, the fast reconnection mechanism evolves most effectively as a nonlinear instability and is sustained steadily. It is concluded in general three-dimensional situations that the fast reconnection mechanism can be realized as an eventual solution for current-driven anomalous resistivities, whereas in usual circumstances with the classical resistivity no substantial magnetic reconnection takes place.

• OSTI ID: 20764528
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 12; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CHARGED-PARTICLE TRANSPORT
CURRENT DENSITY
DIFFUSION
DISTURBANCES
ELECTRON COLLISIONS
ELECTRON TEMPERATURE
ELECTRONS
FEEDBACK
ION DRIFT
ION TEMPERATURE
LAYERS
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
MATHEMATICAL SOLUTIONS
NONLINEAR PROBLEMS
PLASMA
PLASMA SIMULATION
SHOCK WAVES
TEARING INSTABILITY
THREE-DIMENSIONAL CALCULATIONS