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arXiv 1707.08615astro-ph.SR
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第19-23太阳周Rieger型周期的南北不对称性

North-south asymmetry in Rieger-type periodicity during solar cycles 19-23

Eka Gurgenashvili, Teimuraz V. Zaqarashvili, Vasil Kukhianidze, Ramon Oliver, Jose Luis Ballester, Mausumi Dikpati, Scott W. McIntosh

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22 pages, 7 figures
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摘要：

在许多太阳活动周期中，不同的活动指数都表现出里格型周期性。最近表明，周期性与太阳活动有关，在较强的周期中具有较短的周期。太阳活动水平在南北半球之间通常是不对称的，这可能表明在Rieger型周期中存在类似的行为。本文分析了第19-23太阳活动周期间太阳黑子面积/数目和南、北半球总磁通量的资料，这些太阳活动周具有明显的南北不对称性。利用小波分析方法对北半球周期（19-20）内太阳黑子的面积和数量进行了分析，得到了北半球强周期为160-165天，南半球弱周期为180-190天。另一方面，南方主导的周期（21-23）在较强的南半球显示出155-160天的周期性，在较弱的北半球显示出175-188天的周期性。因此，太阳黑子面积/数数据在半球不对称性较强的太阳活动周中，存在南北不对称的Rieger型周期。我们认为这种周期性是由内部发电机层中的磁Rossby波引起的。利用磁Rossby波的频散关系和观测到的Rieger周期性，我们估计该层中的磁场强度强度在较活跃的半球（北在第19-20个周期，南在第21-23个周期）为45-49 kG，在较弱的半球为33-40 kG。半球场强的估计差异约为10 kG，这对发电机模型提出了挑战。第20-23周期的总磁通量数据显示，没有明显的南北不对称性，这需要在未来加以解释。

英文摘要：

Rieger-type periodicity has been detected in different activity indices over many solar cycles. It was recently shown that the periodicity correlates with solar activity having a shorter period during stronger cycles. Solar activity level is generally asymmetric between northern and southern hemispheres, which could suggest the presence of a similar behavior in the Rieger-type periodicity. We analyse the sunspot area/number and the total magnetic flux data for northern and southern hemispheres during solar cycles 19-23 which had remarkable north-south asymmetry. Using wavelet analysis of sunspot area and number during the north-dominated cycles (19-20) we obtained the periodicity of 160-165 days in the stronger northern hemisphere and 180-190 days in the weaker southern hemisphere. On the other hand, south-dominated cycles (21-23) display the periodicity of 155-160 days in the stronger southern hemisphere and 175-188 days in the weaker northern hemisphere. Therefore, the Rieger-type periodicity has the north-south asymmetry in sunspot area/number data during solar cycles with strong hemispheric asymmetry. We suggest that the periodicity is caused by magnetic Rossby waves in the internal dynamo layer. Using the dispersion relation of magnetic Rossby waves and observed Rieger periodicity we estimated the magnetic field strength in the layer as 45-49 kG in more active hemispheres (north during the cycles 19-20 and south during the cycles 21-23) and 33-40 kG in weaker hemispheres. The estimated difference in the hemispheric field strength is around 10 kG, which provides a challenge for dynamo models. Total magnetic flux data during the cycle 20-23 reveals no clear north-south asymmetry which needs to be explained in the future.

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