A statistical analysis of current helicity and twist in solar active regions over the phases of the solar cycle using the spectro-polarimeter data of Hinode
A statistical analysis of current helicity and twist in solar active regions over the phases of the solar cycle using the spectro-polarimeter data of Hinode
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DOI：
10.1093/pasj/psu130
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发表时间：
2014-10
期刊：
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通讯作者：
Ken Otsuji;T. Sakurai;Kirill Kuzanyan Solar Observatory;N. A. Observatory;Mitaka;Tokyo;Department of Materials S
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文献类型：
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作者：
Ken Otsuji;T. Sakurai;Kirill Kuzanyan Solar Observatory;N. A. Observatory;Mitaka;Tokyo;Department of Materials S
太阳磁场的电流螺旋度和扭转度是表征太阳对流区发电机机制的重要参数。我们对Hinode太阳光学望远镜(SOT)的光谱偏振仪(SP)观测到的太阳活动区的当前螺旋度进行了统计研究。我们使用了2006年至2012年共80个活动区的558个矢量磁图的SOT-SP数据。我们应用了空间平滑和将数据点划分为弱场和强场范围，以比较不同尺度和场强的贡献。我们发现，当考虑弱磁场(绝对场强$<；300$Gauss)且不进行平滑处理时，电流螺旋度遵循所谓的半球符号规则。另一方面，当考虑较强的磁场并采用2.0角秒平滑(模拟地面观测)时，电流螺旋度的模式发生波动并违反半球符号规则。此外，我们还发现了弱场和倾斜场更符合的趋势，而强场和垂直场则倾向于违反半球符号规则。这些通过强磁场分量和弱磁场分量产生的螺旋度的不同性质为理解太阳发电机以及太阳活动区的形成和演化机制提供了重要线索。
Current helicity and twist of solar magnetic fields are important quantities to characterize the dynamo mechanism working in the convection zone of the Sun. We have carried out a statistical study on the current helicity of solar active regions observed with the Spectro-Polarimeter (SP) of Hinode Solar Optical Telescope (SOT). We used SOT-SP data of 558 vector magnetograms of a total of 80 active regions obtained from 2006 to 2012. We have applied spatial smoothing and division of data points into weak and strong field ranges to compare the contributions from different scales and field strengths. We found that the current helicity follows the so-called hemispheric sign rule when the weak magnetic fields (absolute field strength $< 300$ gauss) are considered and no smoothing is applied. On the other hand, the pattern of current helicity fluctuates and violates the hemispheric sign rule when stronger magnetic fields are considered and the smoothing of 2.0 arcsec (mimicking ground-based observations) is applied. Furthermore, we found a tendency that the weak and inclined fields better conform to and the strong and vertical fields tend to violate the hemispheric sign rule. These different properties of helicity through the strong and weak magnetic field components give important clues to understanding the solar dynamo as well as the mechanism of formation and evolution of solar active regions.