论文标题
表面通量转运的活性区域的双极近似值如何？
How good is the bipolar approximation of active regions for surface flux transport?
论文作者
论文摘要
我们研究了用双极磁区域（BMR）代表活动区域如何影响表面通量传输模型预测的循环终极场。我们的研究基于一个新的BMR数据库，该数据库在2010年至2020年之间从SDO/HMI活动区域贴片数据中得出。开发了一个自动代码，用于将每个活性区域贴剂与BMR拟合，与该区域的磁通量和轴向偶极矩匹配，并与同一区域的重复观察结果相匹配。通过比较1090 BMR的预测演变与其原始活性区域斑块的预测演变，我们表明双极近似导致净轴向偶极矩的24％高估了相同的流量参数。这是由于忽略许多实际活动区域的更复杂的多极和/或不对称磁性结构而引起的，并且可以解释为什么先前的通量传输模型必须减小BMR倾斜角度以获得逼真的极性场。我们的BMR数据库和用于提取它的Python代码是免费的。
We investigate how representing active regions with bipolar magnetic regions (BMRs) affects the end-of-cycle polar field predicted by the surface flux transport model. Our study is based on a new database of BMRs derived from the SDO/HMI active region patch data between 2010 and 2020. An automated code is developed for fitting each active region patch with a BMR, matching both the magnetic flux and axial dipole moment of the region and removing repeat observations of the same region. By comparing the predicted evolution of each of the 1090 BMRs with the predicted evolution of their original active region patches, we show that the bipolar approximation leads to a 24% overestimate of the net axial dipole moment, given the same flow parameters. This is caused by neglecting the more complex multipolar and/or asymmetric magnetic structures of many of the real active regions, and may explain why previous flux transport models had to reduce BMR tilt angles to obtain realistic polar fields. Our BMR database and the Python code to extract it are freely available.
