**Current accumulation at an asymmetric 3D null point caused by generic shearing motions.** / Galsgaard, K.; Pontin, D. I.

Research output: Contribution to journal › Article

Galsgaard, K & Pontin, DI 2011, 'Current accumulation at an asymmetric 3D null point caused by generic shearing motions' *Astronomy and Astrophysics*, vol 534, A2, pp. -., 10.1051/0004-6361/201117532

Galsgaard, K., & Pontin, D. I. (2011). Current accumulation at an asymmetric 3D null point caused by generic shearing motions. *Astronomy and Astrophysics*, *534*, -. [A2]. 10.1051/0004-6361/201117532

Galsgaard K, Pontin DI. Current accumulation at an asymmetric 3D null point caused by generic shearing motions. Astronomy and Astrophysics. 2011 Oct;534:-. A2. Available from: 10.1051/0004-6361/201117532

@article{864ccd1165094ea1a75f637b2b5162d3,

title = "Current accumulation at an asymmetric 3D null point caused by generic shearing motions",

keywords = "Magnetic reconnection, Magnetohydrodynamics (MHD), Methods: numerical, Sun: corona, Sun: magnetic topology, Topology, Dynamics, Corona, Field",

author = "K. Galsgaard and Pontin, {D. I.}",

year = "2011",

doi = "10.1051/0004-6361/201117532",

volume = "534",

pages = "--",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

}

TY - JOUR

T1 - Current accumulation at an asymmetric 3D null point caused by generic shearing motions

A1 - Galsgaard,K.

A1 - Pontin,D. I.

AU - Galsgaard,K.

AU - Pontin,D. I.

PY - 2011/10

Y1 - 2011/10

N2 - <p>Context. Here we investigate the dynamical evolution of the reconnection process at an initially linear 3D null point that is stressed by a localised shear motion across the spine axis. The difference to previous investigations is that the fan plane is not rotationally symmetric and this allows for different behaviours depending on the alignment of the fan plane relative to the imposed driver direction.</p><p>Aims. The aim is to show how the current accumulation and the associated reconnection process at the non-axisymmetric null depends on the relative orientation between the driver imposed stress across the spine axis of the null and the main eigenvector direction in the fan plane.</p><p>Methods. The time evolution of the 3D null point is investigated solving the 3D non-ideal MHD equations numerically in a Cartesian box. The magnetic field is frozen to the boundaries and the boundary velocity is only non-zero where the imposed driving for stressing the system is applied.</p><p>Results. The current accumulation is found to be along the direction of the fan eigenvector associated with the smallest eigenvalue until the direction of the driver is almost parallel to this eigenvector. When the driving velocity is parallel to the weak eigenvector and has an impulsive temporal profile the null only has a weak collapse forming only a weak current layer. However, when the null point is stressed continuously boundary effects dominates the current accumulation.</p><p>Conclusions. There is a clear relation between the orientation of the current concentration and the direction of the fan eigenvector corresponding to the small eigenvalue. This shows that the structure of the magnetic field is the most important in determining where current is going to accumulate when a single 3D null point is perturbed by a simple shear motion across the spine axis. As the angle between the driving direction and the strong eigenvector direction increases, the current that accumulates at the null becomes progressively weaker.</p>

AB - <p>Context. Here we investigate the dynamical evolution of the reconnection process at an initially linear 3D null point that is stressed by a localised shear motion across the spine axis. The difference to previous investigations is that the fan plane is not rotationally symmetric and this allows for different behaviours depending on the alignment of the fan plane relative to the imposed driver direction.</p><p>Aims. The aim is to show how the current accumulation and the associated reconnection process at the non-axisymmetric null depends on the relative orientation between the driver imposed stress across the spine axis of the null and the main eigenvector direction in the fan plane.</p><p>Methods. The time evolution of the 3D null point is investigated solving the 3D non-ideal MHD equations numerically in a Cartesian box. The magnetic field is frozen to the boundaries and the boundary velocity is only non-zero where the imposed driving for stressing the system is applied.</p><p>Results. The current accumulation is found to be along the direction of the fan eigenvector associated with the smallest eigenvalue until the direction of the driver is almost parallel to this eigenvector. When the driving velocity is parallel to the weak eigenvector and has an impulsive temporal profile the null only has a weak collapse forming only a weak current layer. However, when the null point is stressed continuously boundary effects dominates the current accumulation.</p><p>Conclusions. There is a clear relation between the orientation of the current concentration and the direction of the fan eigenvector corresponding to the small eigenvalue. This shows that the structure of the magnetic field is the most important in determining where current is going to accumulate when a single 3D null point is perturbed by a simple shear motion across the spine axis. As the angle between the driving direction and the strong eigenvector direction increases, the current that accumulates at the null becomes progressively weaker.</p>

KW - Magnetic reconnection

KW - Magnetohydrodynamics (MHD)

KW - Methods: numerical

KW - Sun: corona

KW - Sun: magnetic topology

KW - Topology

KW - Dynamics

KW - Corona

KW - Field

U2 - 10.1051/0004-6361/201117532

DO - 10.1051/0004-6361/201117532

M3 - Article

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

VL - 534

SP - -

ER -