On the Solar Cycle Variation of the Hemispheric Helicity Rule
On the Solar Cycle Variation of the Hemispheric Helicity Rule
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DOI：
10.1086/533435
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发表时间：
2008-04
期刊：
影响因子：
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通讯作者：
A. Pevtsov;R. Canfield;T. Sakurai;M. Hagino
中科院分区：
文献类型：
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作者：
A. Pevtsov;R. Canfield;T. Sakurai;M. Hagino
我们研究了观测到的太阳活动区半球螺旋度规律的时间变化的统计意义，用最佳拟合线性力-自由场参数dα/dφ的纬度梯度来测量。利用四种不同矢量磁图的数据，我们计算并比较了这些仪器从太阳周期21、22和23开始的19年的年平均dα/dφ值。我们发现，尽管每种仪器在某些年份显示半球规则的“错误”标志，但在哪些年份异常的仪器之间没有一致意见。4个数据集的dα/dφ年值与半球螺旋度规律的偏差均不超过3 σ。我们的结论是，由于半球螺旋度规则是一个具有显著分散的弱趋势，活跃区域的年度子集可能产生统计上不可靠的结果。
We study the statistical significance of observed temporal variations of the solar active-region hemispheric helicity rule, as measured by the latitudinal gradient of the best-fit linear force-free-field parameter, dα/dφ . Using data from four different vector magnetographs, we compute and compare average annual dα/dφ values for these instruments for 19 years from solar cycles 21, 22, and 23. We find that although every instrument shows the “wrong” sign for the hemispheric rule in some years, there is no agreement among the instruments on which years are abnormal. None of the four data sets shows annual values of dα/dφ departing from the hemispheric helicity rule by more than 3 σ. We conclude that because the hemispheric helicity rule is a weak tendency with significant scatter, an annual subset of active regions is likely to produce statistically unreliable results.