Helicity patterns of the active regions connected by transequatorial loops

被引:9
作者
Chen, Jie [1 ]
Bao, Shudong [1 ]
Zhang, Hongqi [1 ]
机构
[1] Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
基金
中国国家自然科学基金;
关键词
D O I
10.1007/s11207-007-0284-9
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Using photospheric vector magnetograms of the Huairou Solar Observing Station and coronal X-ray images from the Yohkoh Soft X-Ray Telescope, we calculate the helicity patterns of 43 pairs of active regions and the chirality of 50 pairs of opposite magnetic polarity regions that are connected by transequatorial loops (TLs). To make the results more convincing, two helicity proxies including the local current helicity h (c) and the force-free factor alpha(best) are computed. The results, which are similar for both parameters, are as follows: (1) Current helicity of the active regions pairs connected by transequatorial loops have no obvious regularity: About 50% of the active region pairs carry the same current helicity sign and about 50% of them have the opposite. (2) If we consider the magnetic polarity pairs connected by the TLs, the result is almost the same as that for the active region pairs, with a little more than half of them showing the same chirality. We also make linear force-free extrapolations for 33 TLs and determine their force-free parameter alpha by comparing extrapolated field lines to X-ray images of the TLs. Out of the 19 cases when the footpoints of the TLs have the same current helicity sign, we find that the sign of alpha of the TLs is the same as the sign of the current helicity in the footpoints in 12 cases, whereas it is of opposite sign in 4 cases, and in 3 cases the TLs were found to be potential.
引用
收藏
页码:65 / 85
页数:21
相关论文
共 24 条
[1]   Analysis of electric current helicity in active regions on the basis of vector magnetograms [J].
Abramenko, VI ;
Wang, TJ ;
Yurchishin, VB .
SOLAR PHYSICS, 1996, 168 (01) :75-89
[2]  
Ai Guo-xiang, 1982, Acta Astronomica Sinica, V23, P39
[3]  
Ai Guo-xiang, 1986, Acta Astronomica Sinica, V27, P173
[4]   Patterns of current helicity for solar cycle 22 [J].
Bao, SD ;
Zhang, HQ .
ASTROPHYSICAL JOURNAL, 1998, 496 (01) :L43-L46
[5]  
Canfield R. C., 1996, Astronomical Society of the Pacific Conference Series, V111, P341
[6]   A statistical study of transequatorial loops [J].
Chen, Jie ;
Bao, Shudong ;
Zhang, Hongqi .
SOLAR PHYSICS, 2006, 235 (1-2) :281-294
[7]   EXACT GREENS FUNCTION METHOD OF SOLAR FORCE-FREE MAGNETIC-FIELD COMPUTATIONS WITH CONSTANT ALPHA .1. THEORY AND BASIC TEST CASES [J].
CHIU, YT ;
HILTON, HH .
ASTROPHYSICAL JOURNAL, 1977, 212 (03) :873-885
[8]   Locations of footpoints of transequatorial interconnecting loops [J].
Fárník, F ;
Karlicky, M ;
Svestka, Z .
SOLAR PHYSICS, 2001, 202 (01) :81-97
[9]   Long transequatorial interconnecting loops of the new solar cycle [J].
Fárník, F ;
Karlicky, M ;
Svestka, Z .
SOLAR PHYSICS, 1999, 187 (01) :33-44
[10]   Latitude variation of helicity in solar active regions [J].
Hagino, M ;
Sakurai, T .
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 2004, 56 (05) :831-843