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Twist of magnetic fields in solar active regions
Zhang, HQ; Bao, SD; Kuzanyan, KM
2002-05-01
发表期刊ASTRONOMY REPORTS
卷号46期号:5页码:424-434
摘要We study the twist properties of photospheric magnetic fields in solar active regions using magnetographic data on 422 active regions obtained at the Huairou Solar Observing Station in 1988-1997. We calculate the mean twist (force-free field alpha(f)) of the active regions and compare it with the mean current-helicity density of these same active regions, h(c) = B(parallel to) (.) (del x B)(parallel to). The latitude and longitude distributions and time dependence of these quantities is analyzed. These parameters represent two different tracers of the a effect in dynamo theory, so we might expect them to possess similar properties. However, apart from differences in their definitions, they also display differences associated with the technique used to recalculate the magnetographic data and with their different physical meanings. The distributions of the mean alpha(f) and h(c), both show hemispherical asymmetry-negative (positive) values in the northern (southern) hemisphere-although this tendency is stronger for h(c), One reason for these differences may be the averaging procedure, when twists of opposite sign in regions with weak fields make a small contribution to the mean current-helicity density. Such transequatorial regularity is in agreement with the expectations of dynamo theory. In some active regions, the average alpha(f) and h(c), do not obey this transequatorial rule. As a whole, the mean twist of the magnetic fields alpha(f) of active regions does not vary significantly with the solar cycle. Active regions that do not follow the general behavior for alpha(f) do not show any appreciable tendency to cluster at certain longitudes, in contrast to results for h, noted in previous studies. We analyze similarities and differences in the distributions of these two quantities. We conclude that using only one of these tracers, such as alpha(f), to search for signatures of the alpha effect can have disadvantages, which should be taken into account in future studies. (C) 2002 MAIK "Naukalltiterperiodica".
收录类别SCI
语种英语
WOS记录号WOS:000176054700009
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文献类型期刊论文
条目标识符http://ir.bao.ac.cn/handle/114a11/8556
专题太阳物理研究部
作者单位1.Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
2.Inst Terr Magnetism Ionosphere & Radiowave Propag, Heliophys Lab, Troitsk 142190, Moscow Region, Russia
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Zhang, HQ,Bao, SD,Kuzanyan, KM. Twist of magnetic fields in solar active regions[J]. ASTRONOMY REPORTS,2002,46(5):424-434.
APA Zhang, HQ,Bao, SD,&Kuzanyan, KM.(2002).Twist of magnetic fields in solar active regions.ASTRONOMY REPORTS,46(5),424-434.
MLA Zhang, HQ,et al."Twist of magnetic fields in solar active regions".ASTRONOMY REPORTS 46.5(2002):424-434.
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