The Rise of a Magnetic Flux Tube in a Background Field: Solar Helicity Selection Rules
The Rise of a Magnetic Flux Tube in a Background Field: Solar Helicity Selection Rules
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DOI：
10.3847/2041-8213/aac723
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
B. Manek;N. Brummell;Dongwoo Lee
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文献类型：
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作者：
B. Manek;N. Brummell;Dongwoo Lee
磁场从太阳内部向表面的浮力传输在活动区的出现、黑子的形成和整个太阳发电机中起着重要作用。观测表明，环形通量集中，通常被称为“通量管”，上升从他们的区域开始可能在太阳速跃层向太阳表面由于磁浮力。许多研究都假设存在这样的磁结构，并研究了一个孤立的磁通管在一个静止的，无场的环境中的浮力上升。在这里，出于磁通管形成的机制，我们放松后一个假设，并研究嵌入在一个大规模的极向背景磁场的环形磁通管的崛起。我们发现大尺度背景场的存在严重影响了上升管的动力学特性。一个相对较弱的背景场，低至管强度的6%，可以破坏在没有背景场的情况下会上升的管的上升。令人惊讶的是，具有一个扭曲符号的管的上升被比另一个明显更弱的背景场抑制。这表明了一个潜在的机制，为选择的首选螺旋度的上升和新兴的太阳能管的情况下，是相称的半球形规则的许多功能。
The buoyant transport of magnetic fields from the solar interior toward the surface plays an important role in the emergence of active regions, the formation of sunspots, and the overall solar dynamo. Observations suggest that toroidal flux concentrations, often referred to as “flux tubes,” rise from their region of initiation likely in the solar tachocline toward the solar surface due to magnetic buoyancy. Many studies have assumed the existence of such magnetic structures and studied the buoyant rise of an isolated flux tube in a quiescent, field-free environment. Here, motivated by the mechanisms of flux tube formation, we relax the latter assumption and study the rise of a toroidal flux tube embedded in a large-scale poloidal background magnetic field. We find that the presence of the large-scale background field severely affects the dynamics of the rising tube. A relatively weak background field, as low as 6% of the tube strength, can destroy the rise of a tube that would otherwise rise in the absence of the background field. Surprisingly, the rise of tubes with one sign of the twist is suppressed by a significantly weaker background field than the other. This demonstrates a potential mechanism for the selection of the preferred helicity of rising and emerging tubes for the solar case that is commensurate with many features of the hemispherical rule.