A solar eruption triggered by merge interactions of different helicity loops

Abstract

Aims: We investigate the magnetic evolution of a flare/CME source region to determine the trigger of the flare and the EUV brightening event. Also, we discuss the role of the current helicity (h_c) in solar activity.
Methods: We use the long duration sequences of SOHO/MDI magnetograms and TRACE 195 Å images for a super active region (AR), NOAA AR 8375. Magnetic field changes in the photosphere and the corona are investigated.
Results: In AR 8375, the southwestern and northwestern parts of an overlying loop (h_c < 0) are influenced by the rising magnetic arcades (h_c > 0) and the emerging flux region (h_c > 0). Two collisions make the overlying loop inflate in a bounce interaction. However, the related solar events are triggered by a merge interaction which takes place among the fibers of the rising magnetic arcades and among those of the overlying loop.