MAGNETIC BRAIDING AND QUASI-SEPARATRIX LAYERS

被引:42
作者
Wilmot-Smith, A. L. [1 ]
Hornig, G. [1 ]
Pontin, D. I. [1 ]
机构
[1] Univ Dundee, Div Math, Dundee DD1 4HN, Scotland
关键词
magnetic fields; MHD; Sun: corona; HYPERBOLIC FLUX TUBES; CURRENT SHEET FORMATION; SOLAR CORONA; FIELDS; RECONNECTION; EXISTENCE; DRIVEN; MODEL;
D O I
10.1088/0004-637X/704/2/1288
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The squashing factor Q, a property of the magnetic field line mapping, has been suggested as an indicator for the formation of current sheets, and subsequently magnetic reconnection, in astrophysical plasmas. Here, we test this hypothesis for a particular class of braided magnetic fields which serve as a model for solar coronal loops. We explore the relationship between quasi-separatrix layers (QSLs), that is, layer-like structures with high Q value, electric currents, and integrated parallel currents; the latter being a quantity closely related to the reconnection rate. It is found that as the degree of braiding of the magnetic field is increased, the maximum values of Q increase exponentially. At the same time, the distribution of Q becomes increasingly filamentary, with the width of the high-Q layers exponentially decreasing. This is accompanied by an increase in the number of layers so that as the field is increasingly braided the volume becomes occupied by a myriad of thin QSLs. QSLs are not found to be good predictors of current features in this class of braided fields. Indeed, despite the presence of multiple QSLs, the current associated with the field remains smooth and large scale under ideal relaxation; the field dynamically adjusts to a smooth equilibrium. Regions of high Q are found to be better related to regions of high integrated parallel current than to actual current sheets.
引用
收藏
页码:1288 / 1295
页数:8
相关论文
共 24 条
[1]   Current sheet formation in quasi-separatrix layers and hyperbolic flux tubes [J].
Aulanier, G ;
Pariat, E ;
Démoulin, P .
ASTRONOMY & ASTROPHYSICS, 2005, 444 (03) :961-976
[2]   EXISTENCE OF FORCE-FREE MAGNETIC-FIELDS [J].
BINEAU, M .
COMMUNICATIONS ON PURE AND APPLIED MATHEMATICS, 1972, 25 (01) :77-&
[3]   The Parker problem and the theory of coronal heating [J].
Craig, IJD ;
Sneyd, AD .
SOLAR PHYSICS, 2005, 232 (1-2) :41-62
[4]   A DYNAMIC RELAXATION TECHNIQUE FOR DETERMINING THE STRUCTURE AND STABILITY OF CORONAL MAGNETIC-FIELDS [J].
CRAIG, IJD ;
SNEYD, AD .
ASTROPHYSICAL JOURNAL, 1986, 311 (01) :451-459
[5]  
Demoulin P, 1996, ASTRON ASTROPHYS, V308, P643
[6]   A relationship between transition region brightenings, abundances, and magnetic topology [J].
Fletcher, L ;
Fuentes, MCL ;
Mandrini, CH ;
Schmieder, B ;
Démoulin, P ;
Mason, HE ;
Young, PR ;
Nitta, N .
SOLAR PHYSICS, 2001, 203 (02) :255-287
[7]   Magnetic pinching of hyperbolic flux tubes. II. Dynamic numerical model [J].
Galsgaard, K ;
Titov, VS ;
Neukirch, T .
ASTROPHYSICAL JOURNAL, 2003, 595 (01) :506-516
[8]   Heating and activity of the solar corona .1. Boundary shearing of an initially homogeneous magnetic field [J].
Galsgaard, K ;
Nordlund, A .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 1996, 101 (A6) :13445-13460
[9]   Dynamical investigation of three-dimensional reconnection in quasi-separatrix layers in a boundary-driven magnetic field [J].
Galsgaard, K .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2000, 105 (A3) :5119-5134
[10]   A THEORETICAL FOUNDATION OF GENERAL MAGNETIC RECONNECTION [J].
HESSE, M ;
SCHINDLER, K .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 1988, 93 (A6) :5559-5567