A statistical study of trans-equatorial loops from 2006 to 2020

Abstract

ABSTRACT We studied trans-equatorial loops (TLs) statistically from December 2006 to 2020. During this period, 160 TLs were identified, and 12 per cent of all active regions are connected by TLs. The result shows that 74 per cent of TLs are connected to regions of preceding magnetic polarity (PTLs), and only 26 per cent of TLs are connected to regions of following magnetic polarity (FTLs). The dominance of PTLs is related to Joy’s law. Moreover, the average length of TLs is 20°, and their lengths decrease during the solar cycle. By comparing the number of TLs and the smoothed monthly mean number of sunspots from 2009 to 2018, 88 per cent of the TLs appeared near the solar maximum (2014 ± 2). We noted that the closer a sunspot is to the equator, the easier it is for a TL to form. Furthermore, the tilt angle and latitudinal asymmetry of TL foot-points are independent of the solar cycle.