New Evidence for the Role of Emerging Flux in a Solar Filament’s Slow Rise Preceding Its CME‐producing Fast Eruption

We observe the eruption of a large-scale ( 300,000 km) quiet-region solar filament leading to an Earth-directed ‘‘halo’’ coronal mass ejection (CME), using data from EIT, CDS, MDI, and LASCO on SOHO and from SXT on Yohkoh. Initially the filament shows a slow ( 1k m s 1 projected against the solar disk) and approximately constant velocityriseforabout6hr,beforeeruptingrapidly,reachingavelocityof 8kms 1 overthenext 25minutes.CDS Doppler data show Earth-directed filament velocities ranging from <20 km s 1 (the noise limit) during the slow-rise phase, to 100 km s 1 early in the eruption. Beginning within 10 hr prior to the start of the slow rise, localized new magneticfluxemergednearoneendofthefilament.Nearthestartofandduringtheslow-risephase,softX-ray(SXR) microflaring occurred repeatedly at the flux-emergence site, and the magnetic arcade over the filament progressively brightened in a fan of illumination in SXRs. These observations are consistent with ‘‘tether-weakening’’ reconnection occurring between the newly emerging flux and the overlying arcade field containing the filament, and apparently this reconnection is the cause of the filament’s slow rise. We cannot, however, discern whether the transition from slow rise to fast eruption was caused by a final episode of tether-weakening reconnection, or by one or some combination of otherpossiblemechanismsallowedbytheobservations.Intensity‘‘dimmings’’and‘‘brightenings’’occurringbothnear to and relatively far from the location of the filament are possible signatures ofthe expansion (‘‘opening’’) of the erupting field and its reconnection with overarching field during the eruption.