Degree of electric current neutralization and the activity in solar active regions
Degree of electric current neutralization and the activity in solar active regions
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DOI：
10.1093/mnras/stz1020
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发表时间：
2019-04
影响因子：
4.8
通讯作者：
P. Vemareddy
中科院分区：
文献类型：
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作者：
P. Vemareddy
利用日震和磁成像仪的时间序列矢量磁场观测资料，研究了20个太阳活动区（AR）的非中性电流与观测活动的关系。在给定的磁极性下的净电流是直流电流（DC）和返回电流（RC）的代数和，并且比率|DC/RC|是净电流中和度（NCN）的量度。在新兴的AR中，这些电流的非中性随着磁通出现的开始而建立，在双极区域的分离运动期间松弛到中性。因此，一些新兴的AR是发生在更高级别的非中性时期的CME的源区。在出现后阶段的AR可以是CME生产力，提供他们有相互作用的两极地区的收敛和剪切运动。在这些情况下，净电流以更高的非中性水平（>1.3）演变。显然，|DC/RC|在闪耀和安静的AR中，变化接近于1。在所有AR样本中，|DC/RC|手征电流密度下的平均电流密度比垂直电流密度下的平均电流密度高。由于非中和电流产生于剪切极性反转线附近，因此SPIL段的总长度和NCN程度的剖面彼此遵循正相关。我们发现，SPIL是本地化的小片段在flaring-ARs，而它是长连续的CME生产的AR。这些观测结果表明CME和耀斑之间的分界线，其区别在于AR中反映在非中性电流中的磁剪切的全局或局部性质。
Using time-sequence vector magnetic field observation from Helioseismic and Magnetic Imager, we examined the connection of non-neutralized currents and the observed activity in 20 solar active regions (ARs). The net current in a given magnetic polarity is algebraic sum of direct current (DC) and return current (RC) and the ratio |DC/RC| is a measure of degree of net current neutralization (NCN). In the emerging ARs, the non-neutrality of these currents builds with the onset of flux emergence, following the relaxation to neutrality during the separation motion of bipolar regions. Accordingly, some emerging ARs are source regions of CMEs occurring at the time of higher level non-neutrality. ARs in the post-emergence phase can be CME productive provided they have interacting bipolar regions with converging and shearing motions. In these cases, the net current evolves with higher level (>1.3) of non-neutrality. Differently, the |DC/RC| in flaring and quiet ARs vary near unity. In all the AR samples, the |DC/RC| is higher for chiral current density than that for vertical current density. Owing to the fact that the non-neutralized currents arise in the vicinity of sheared polarity-inversion-lines (SPILs), the profiles of the total length of SPIL segments and the degree of NCN follow each other with a positive correlation. We find that the SPIL is localized as small segments in flaring-ARs, whereas it is long continuous in CME-producing ARs. These observations demonstrate the dividing line between the CMEs and flares with the difference being in global or local nature of magnetic shear in the AR that reflected in non-neutralized currents.