Non-linear Tearing of 3D Null Point Current Sheets

Abstract

The manner in which the rate of magnetic reconnection scales with the Lundquist number in realistic three-dimensional (3D) geometries is still an unsolved problem. It has been demonstrated that in 2D rapid non-linear tearing allows the reconnection rate to become almost independent of the Lundquist number (the `plasmoid instability'). Here we present the first study of an analogous instability in a fully 3D geometry, defined by a magnetic null point. The 3D null current layer is found to be susceptible to an analogous instability, but is marginally more stable than an equivalent 2D Sweet-Parker-like layer. Tearing of the sheet creates a thin boundary layer around the separatrix surface, contained within a flux envelope with a hyperbolic structure that mimics a spine-fan topology. Efficient mixing of flux between the two topological domains occurs as the flux rope structures created during the tearing process evolve within this envelope. This leads to a substantial increase in the rate of reconnection between the two domains.

Submitted to Physics of Plasmas (11 pages, 9 figures)

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• Dynamic Topology and Flux Rope Evolution During Non-linear Tearing of 3D Null Point Current Sheets
• The effect of reconnection on the structure of the Sun's open-closed-flux boundary
• The structure of current layers and degree of field line braiding in coronal loops
• Formation and Reconnection of Three-dimensional Current Sheets with a Guide Field in the Solar Corona
• 2010 August 1-2 sympathetic eruptions: II. Magnetic topology of the MHD background field
• Evolution, structure and topology of self-generated turbulent reconnection layers
• A comparison of methods for finding magnetic nulls in simulations and in situ observations of space plasmas
• Is Magnetic Topology Important for Heating the Solar Atmosphere?
• The plasmoid instability in a confined solar flare