Letter to the Editor

A solar eruption triggered by merge interactions of different helicity loops

SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, PR China e-mail: [wbsong;fengx;fshen]@spaceweather.ac.cn

Received: 20 March 2008
Accepted: 9 May 2008

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 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.