Helicity Observations of Weak and Strong Fields
Helicity Observations of Weak and Strong Fields
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DOI：
10.1086/506560
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发表时间：
2006-06
期刊：
影响因子：
--
通讯作者：
Mei Zhang
中科院分区：
文献类型：
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作者：
Mei Zhang
我们在这封信中报告了我们对光球矢量磁场测量大样本的分析。我们的样本由中国国家天文台怀柔太阳观测站从1997年1月到2004年8月获得的17,200个矢量磁图组成。计算了α和电流螺旋度两个物理量，并研究了它们的符号和振幅，以寻找太阳活动周的变化。与同类型的其他研究不同，我们分别计算了弱（100 G 1000 G）场的这些量。对于弱场，我们发现在太阳活动周的大多数年份，α和电流螺旋度的符号都符合已建立的半球规则，它们的大小随着太阳活动周的发展大致呈减小的趋势。强场的分析给出了一个有趣的结果：α和电流螺旋度都呈现与弱场相反的符号。发电机理论和螺旋度生产这些意见的影响也进行了简要讨论。
We report in this Letter our analysis of a large sample of photospheric vector magnetic field measurements. Our sample consists of 17,200 vector magnetograms obtained from 1997 January to 2004 August by the Huairou Solar Observing Station of the Chinese National Astronomical Observatory. Two physical quantities, α and current helicity, are calculated, and their signs and amplitudes are studied in a search for solar cycle variations. Differently from other studies of the same type, we calculate these quantities for weak (100 G 1000 G) fields separately. For weak fields, we find that the signs of both α and current helicity are consistent with the established hemispheric rule during most years of the solar cycle and that their magnitudes show a rough tendency of decreasing with the development of the solar cycle. The analysis of strong fields gives an interesting result: both α and current helicity present a sign opposite to that of weak fields. The implications of these observations for dynamo theory and helicity production are also briefly discussed.