Energy buildup of multipolar magnetic fields by photospheric shear motion

被引:28
作者
Hu, YQ [1 ]
机构
[1] Univ Sci & Technol China, Sch Earth & Space Sci, Hefei 230026, Anhui, Peoples R China
关键词
Sun : corona; Sun : magnetic fields;
D O I
10.1086/383517
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Using an axisymmetrical ideal magnetohydrodynamic (MHD) model in spherical coordinates, we present a numerical study of the energy buildup of coronal magnetic fields by photospheric shear motions. The unsheared potential field consists of a dipolar and an octopolar component with a neutral point somewhere at the equator. The separatrix crossing the neutral point divides the field into four topologically disconnected regions: a central arcade astride the equator, a bipolar field on each side of the central arcade, and an overlying arcade above the separatrix. A specific type of photospheric shearing is then introduced at the base of the central arcade, and the energy of the resultant sheared field is calculated. It is found for this special case that the magnetic energy of the sheared force-free field cannot exceed that of the corresponding partly open field in which the central and overlying arcades become fully open but the bipolar fields at the flank remain closed. This inspires us to extend Aly's conjecture from fully open force-free fields to partly open ones in such a way that in the frame of ideal MHD, it is impossible to store more magnetic energy in the corona by photospheric shear motions at the base of any part of the closed flux of a force-free field than that of the field in which the sheared closed flux opens but the remainder remains closed.
引用
收藏
页码:1032 / 1038
页数:7
相关论文
共 24 条
[1]   ON SOME PROPERTIES OF FORCE-FREE MAGNETIC-FIELDS IN INFINITE REGIONS OF SPACE [J].
ALY, JJ .
ASTROPHYSICAL JOURNAL, 1984, 283 (01) :349-362
[2]   HOW MUCH ENERGY CAN BE STORED IN A 3-DIMENSIONAL FORCE-FREE MAGNETIC-FIELD [J].
ALY, JJ .
ASTROPHYSICAL JOURNAL, 1991, 375 (02) :L61-L64
[3]  
ALY JJ, 1994, ASTRON ASTROPHYS, V288, P1012
[4]   Very fast opening of a three-dimensional twisted magnetic flux tube [J].
Amari, T ;
Luciani, JF ;
Aly, JJ ;
Tagger, M .
ASTROPHYSICAL JOURNAL, 1996, 466 (01) :L39-+
[5]   A model for solar coronal mass ejections [J].
Antiochos, SK ;
DeVore, CR ;
Klimchuk, JA .
ASTROPHYSICAL JOURNAL, 1999, 510 (01) :485-493
[6]   THEORY OF ONSET OF SOLAR ERUPTIVE PROCESSES [J].
BIRN, J ;
GOLDSTEIN, H ;
SCHINDLER, K .
SOLAR PHYSICS, 1978, 57 (01) :81-101
[7]   Energy of force-free magnetic fields in relation to coronal mass ejections [J].
Choe, GS ;
Cheng, CZ .
ASTROPHYSICAL JOURNAL, 2002, 574 (02) :L179-L182
[8]   A review on the genesis of coronal mass ejections [J].
Forbes, TG .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2000, 105 (A10) :23153-23165
[9]   Equilibrium and catastrophe of coronal flux ropes in axisymmetrical magnetic field [J].
Hu, YQ ;
Li, GQ ;
Xing, XY .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2003, 108 (A2)
[10]   A MULTISTEP IMPLICIT SCHEME FOR TIME-DEPENDENT TWO-DIMENSIONAL MAGNETOHYDRODYNAMIC FLOWS [J].
HU, YQ .
JOURNAL OF COMPUTATIONAL PHYSICS, 1989, 84 (02) :441-460