The Source of a coronal mass ejection in a decayed solar active region

Abstract

We have studied the source of a coronal mass ejection (CME), which occurred in a decayed active region NOAA 7978 on 19 October, 1996. The active region NOAA 7978 first appeared on the solar disk on 2 June, 1996 and made more than five disk passages before it decayed. The event analysed in this paper was observed during fifth disk passage. We have attempted to identify the mechanism responsible for triggering this CME based on the analysis of photospheric magnetograms (MDI/SoHO), chromospheric filtergrams (Meudon and Big Bear Observatories) and coronal images (SXT/Yohkoh). We found that the emergence of new bipoles in the active region led to the eruption of a low-lying sheared filament observed in SXT images, subsequently followed by filament eruption observed both in H α and EUV wavelengths (EIT/SoHO). The study aims at chronologically investigating the occurrence of the events in different wavelengths, in order to have a comprehensive understanding of the mechanism involved in the launch of the CME.