Current sheets at three-dimensional magnetic nulls: Effect of compressibility

Abstract

The nature of current sheet formation in the vicinity of three-dimensional (3D) magnetic null points is investigated. The particular focus is upon the effect of the compressibility of the plasma on the qualitative and quantitative properties of the current sheet. An initially potential 3D null is subjected to shearing perturbations, as in a previous paper [Pontin et al., Phys. Plasmas, in press (2007)]. It is found that as the incompressible limit is approached, the collapse of the null point is suppressed, and an approximately planar current sheet aligned to the fan plane is present instead. This is the case regardless of whether the spine or fan of the null is sheared. Both the peak current and peak reconnection rate are reduced. The results have a bearing on previous analytical solutions for steady-state reconnection in incompressible plasmas, implying that fan current sheet solutions are dynamically accessible, while spine current sheet solutions are not.

to appear in Physics of Plasmas. This version contains updated figures and references, additional discussion, and typos are fixed. This is the second in a series of papers - the first of which (by the same authors) is located at astro-ph/0701462. A version with higher quality figures can be found at http://www.maths.dundee.ac.uk/~dpontin/

References in corpus (4)

• In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail
• Current amplification and magnetic reconnection at a 3D null point. I - Physical characteristics
• The Magnetic Topology of Coronal Mass Ejection sources
• Current sheet formation and non-ideal behaviour at three-dimensional magnetic null points

Cited by in corpus (13)

• Plasma Jets and Eruptions in Solar Coronal Holes: a 3D flux emergence experiment
• Three-dimensional magnetic reconnection regimes: A review
• 3D Null Point Reconnection Regimes
• On the nature of reconnection at a solar coronal null point above a separatrix dome
• On the 2012 October 23 circular ribbon flare: emission features and magnetic topology
• Theory of magnetic reconnection in solar and astrophysical plasmas
• Solar Particle Acceleration at Reconnecting 3D Null Points
• Steady state reconnection at a single 3D magnetic null point
• Current accumulation at an asymmetric 3D null point caused by generic shearing motions
• Dynamical Relaxation of Coronal Magnetic Fields. III. 3D Spiral Nulls
• Kelvin-Helmholtz instability in a current-vortex sheet at a 3D magnetic null
• Localised acceleration of energetic particles by a weak shock in the solar corona
• Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection