Transequatorial Loops in the Solar Corona

Abstract

Using X-ray coronal images, full-disk longitudinal magnetograms, and vector magnetograms of active regions, we study active regions connected across the solar equator. We survey the Yohkoh data set between 1991 October and 1998 December and find 87 transequatorial loop systems (TLSs). We classify these loops in four different categories and study a separation between regions, their rotation rates, and the sign of the current helicity (chirality) of the magnetic fields. We find that approximately one-third of all active regions on the Sun exhibit transequatorial loops. The fraction of TLSs is solar-cycle independent. Transequatorial loops may develop between existing active regions or between mature regions and new magnetic flux shortly after flux emergence. Observations suggest, however, that formation of TLSs is not a random process—a connection between two areas may exist well before the reconnection takes place. We find that the reconnected regions have approximately the same rotation rate and tend to appear on certain longitudes, similar to the complexes of activity. In most cases transequatorial interconnected regions have the same handedness of their magnetic field.