Degree of electric current neutralization and the activity in solar Active Regions

Abstract

Using time-sequence vector magnetic field observation from \textit{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.

12 pages, 6 figures, accepted to publish in MNRAS

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• Investigating pre-eruptive magnetic properties at the footprints of erupting magnetic flux ropes
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• Oscillatory reconnection and waves driven by merging magnetic flux ropes in solar flares
• What Are the Causes of Super Activity of Solar Active Regions?
• Successive Injection of Opposite Magnetic Helicity: Evidence for Active Regions without Coronal Mass Ejections
• The extremely strong non-neutralized electric currents of the unique solar active region NOAA 13664
• Non-Neutralized Electric Current of Active Regions Explained as a Projection Effect
• Nature of helicity injection in non-erupting solar active regions
• Confinedness of an X3.1 class solar flare occurred in NOAA 12192: Analysis from multi-instruments observations