Multi-wavelength observations of the onset phase of a coronal mass ejection

The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are des cribed. The event occurred on the SW limb of the Sun in active region AR 80 26 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Ima ges taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the e mergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the t ime of the flare. Yohkoh images, taken about 15 min later, show that this c avity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an H alpha surge or small filament eruption occurs about 50 arc sec northwards along the lim b from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected b y hot loops near their bases. Both jets disappear within a few minutes of o ne another. Clear evidence of the CME first appeared in the Large Angle Spectrometric C oronagraph (LASCO) and EIT images 40 min after the flare and onset of the f ilament ejection. It seems to come from a region between the two X-ray jets . This leads to the speculation that magnetic field reconnection near one f ootpoint of a loop system triggers reconnection near its other footpoint. T he loop system is destabilized and ultimately gives rise to the CME. This p ossibility is supported by magnetic field and H alpha images taken when the active region was at disk center which show that the active region had a d ouble bipole structure with dark H alpha filaments between the bipoles.