Current Singularities at Quasi-Separatrix Layers and Three-Dimensional Magnetic Nulls

Abstract

The open problem of how singular current structures form in line-tied, three-dimensional magnetic fields is addressed. A Lagrangian magneto-frictional relaxation method is employed to model the field evolution towards the final near-singular state. Our starting point is an exact force-free solution of the governing magnetohydrodynamic (MHD) equations which is sufficiently general to allow for topological features like magnetic nulls to be inside or outside the computational domain, depending on a simple set of parameters. Quasi-separatrix layers (QSLs) are present in these structures and together with the magnetic nulls, they significantly influence the accumulation of current. It is shown that perturbations affecting the lateral boundaries of the configuration lead not only to collapse around the magnetic null, but also to significant QSL currents. Our results show that once a magnetic null is present, the developing currents are always attracted to that specific location and show a much stronger scaling with resolution than the currents which form along the QSL. In particular, the null point scalings can be consistent with models of "fast" reconnection. The QSL currents also appear to be unbounded but give rise to weaker singularities, independent of the perturbation amplitude.

6 pages, 6 figures, published in The Astrophysical Journal

References in corpus (8)

• Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona
• Magnetic Pinching of Hyperbolic Flux Tubes: I. Basic Estimations
• Magnetic Reconnection along Quasi-Separatrix Layers as a Driver of Ubiquitous Active Region Outflows
• Recurrent Coronal Jets Induced by Repetitively Accumulated Electric Currents
• Temporal Evolution of the Magnetic Topology of the NOAA Active Region 11158
• Solar Particle Acceleration at Reconnecting 3D Null Points
• Numerical Simulation of Current Sheet Formation in a Quasi-Separatrix Layer using Adaptive Mesh Refinement
• Current singularities in line-tied three-dimensional magnetic fields

Cited by in corpus (10)

• 3D magnetic reconnection and its application to solar flares
• Witnessing a Large-scale Slipping Magnetic Reconnection along a Dimming Channel during a Solar Flare
• Formation of current singularity in a topologically constrained plasma
• Identification of Pre-flare Processes and Their Possible Role in Driving a Large-scale Flux Rope Eruption with Complex M-class Flare in the Active Region NOAA 12371
• Magnetic reconnection and thermal equilibration
• Magnetic reconnection with null and X-points
• Constructing current singularity in a 3D line-tied plasma
• Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection
• Magnetic nulls in interacting dipolar fields
• Variational Integration for Ideal Magnetohydrodynamics and Formation of Current Singularities