Formation of two homologous transequatorial loops

The formation mechanism of two homologous transequatorial loops (TLs) of July 7–8, 1999 (SOL1999-07-07) is studied. The TLs connected active region AR 8614 from the northern hemisphere to AR 8626 in the southern hemisphere. The first TL appeared as a distinct structure at 12:49 UT on July 7, the second TL appeared at 06:21 UT, on July 8. Important results are obtained in this analysis: (i) The configuration of the two TLs is similar in X-rays. (ii) The sizes of the two active regions related to the TLs increased before and during the formation of the two TLs, this induced the expansion of their coronal loops. (iii) Both TLs formed globally on a time scale shorter than 110 min (time resolution of observations). (iv) An X-shaped coronal structure was observed. This observational evidence suggests that the two TLs formed by the same physical mechanism, magnetic reconnection, between the two expanding magnetic configurations of the two ARs.