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arXiv 1609.00329astro-ph.SR
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太阳活动周期中磁舌的性质

Properties of Magnetic Tongues over a Solar Cycle

M. Poisson, P. Démoulin, M. López Fuentes, C. H. Mandrini

摘要:

双极活动区(AR)出射变形过程中的光球主磁极性空间分布被称为磁舌。它们归因于形成AR的环形磁通量管中的扭曲的存在。本文的目的是研究新出现的AR的扭曲从光球视线磁图中观察到的磁舌的演变。我们将Poisson等人(2015,Solar Phys. 290,727)描述的程序应用于在整个太阳周期23和周期24开始时观察到的AR。我们的研究结果表明,使用舌头作为扭曲的代理获得的半球规则具有弱的符号优势(南半球为53%,北半球为58%)。通过定义舌角的变化,我们表征了AR出现的不同阶段的磁舌的强度。我们发现,有一种趋势的舌头是强的出现在开始和变弱的AR达到其最大磁通量。我们比较这种演变与出现的环形磁通绳模型与非均匀扭曲。只有当使用广泛的扭曲轮廓,特别是在垂直于光球的方向上具有各种各样的扭曲梯度时,才能再现所分析的AR中舌头的演变。虽然使用的分析模型是一个特殊的情况下,选择最小化问题的复杂性,所获得的结果设置新的观测约束的理论模型的磁通绳出现,形成双极AR。

英文摘要:

The photospheric spatial distribution of the main magnetic polarities of bipolar active regions (ARs) presents during their emergence deformations are known as magnetic tongues. They are attributed to the presence of twist in the toroidal magnetic flux-tubes that form the ARs. The aim of this article is to study the twist of newly emerged ARs from the evolution of magnetic tongues observed in photospheric line-of-sight magnetograms. We apply the procedure described by Poisson et al. (2015, Solar Phys. 290, 727) to ARs observed over the full Solar Cycle 23 and the beginning of Cycle 24. Our results show that the hemispherical rule obtained using the tongues as a proxy of the twist has a weak sign-dominance (53 % in the southern hemisphere and 58 % in the northern hemisphere). By defining the variation of the tongue angle, we characterize the strength of the magnetic tongues during different phases of the AR emergence. We find that there is a tendency of the tongues to be stronger during the beginning of the emergence and to become weaker as the AR reaches its maximum magnetic flux. We compare this evolution with the emergence of a toroidal flux-rope model with non-uniform twist. The variety of evolution of the tongues in the analyzed ARs can only be reproduced when using a broad range of twist profiles, in particular having a large variety of twist gradient in the direction vertical to the photosphere. Although the analytical model used is a special case, selected to minimize the complexity of the problem, the results obtained set new observational constraints to theoretical models of flux-rope emergence that form bipolar ARs.

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