THE INITIATION OF CORONAL MASS EJECTIONS BY NEWLY EMERGING MAGNETIC-FLUX

We present observational evidence that eruptions of quiescent filament s and associated coronal mass ejections (CMEs) occur as a consequence of the destabilization of large-scale coronal arcades due to interacti ons between these structures and new and growing active regions. Both statistical and case studies have been carried out. In a case study of a ''bugle'' observed by the High-Altitude Observatory Solar Maximum M ission coronagraph, the high-resolution magnetograms from the Big Bear Solar Observatory show newly emerging and rapidly changing flux in th e magnetic fields that apparently underlie the bugle. For other case s tudies and in the statistical work the eruption of major quiescent fil aments was taken as a proxy for CME eruption. We have found that two t hirds of the quiescent-filament-associated CMEs occurred after substan tial amounts of new magnetic flux emerged in the vicinity of the filam ent. In addition, in a study of all major quiescent filaments and acti ve regions appearing in a 2-month period we found that 17 of the 22 fi laments that were associated with new active regions erupted and 26 of the 31 filaments that were not associated with new Aux did not erupt. In all cases in which the new flux was oriented favorably for reconne ction with the preexisting large-scale coronal arcades; the filament w as observed to erupt. The appearance of the new flux in the form of ne w active regions begins a few days before the eruption and typically i s still occurring at the time of the eruption. A CME initiation scenar io taking account of these observational results is proposed.