Steady state reconnection at a single 3D magnetic null point

Abstract

To systematically stress a rotationally symmetric 3D magnetic null point by advecting the opposite footpoints of the spine axis in opposite directions. This stress eventually concentrates in the vicinity of the null point forming a local current sheet through which magnetic reconnection takes place. The aim is to look for a steady state evolution of the current sheet dynamics which may provide scaling relations for various characteristic parameters of the system. The evolution is followed by solving numerically the non-ideal MHD equations in a Cartesian domain. The null point is embedded in an initially constant density and temperature plasma. It is shown that a quasi-steady reconnection process can be set up at a 3D null by continuous shear driving. It appears that a true steady state in unlikely to be realised as the current layer tends to grow until restricted by the geometry of the computational domain and imposed driving profile. However, ratios between characteristic quantities clearly settle after some time to stable values -- so that the evolution is quasi-steady. The experiments show a number of scaling relations, but they do not provide a clear consensus for extending to lower magnetic resistivity or faster driving velocities. More investigations are needed to fully clarify the properties of current sheets at magnetic null points.

9 pages, 11 figures, accepted for publication in A&A

References in corpus (5)

• Nonlinear Fast Magnetoacoustic Wave Propagation in the Neighbourhood of a 2D magnetic X-point: Oscillatory Reconnection
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• Current sheet formation and non-ideal behaviour at three-dimensional magnetic null points
• The Number Of Magnetic Null Points In The Quiet Sun Corona
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• The effect of reconnection on the structure of the Sun's open-closed-flux boundary
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• The behaviour of magnetoacoustic waves in the neighbourhood of a two-dimensional null point: initially cylindrically-symmetric perturbations
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