The Formation of a Prominence in NOAA Active Region 8668. II. Trace Observations of Jets and Eruptions Associated with Canceling Magnetic Features

Our previous study has shown that the formation of a reverse S-shaped filament in NOAA active region 8668 was closely associated with a large canceling magnetic feature. In the present paper we investigate the response of the upper atmosphere at the region of this canceling magnetic feature. The UV and EUV data taken by the Transition Region and Coronal Explorer (TRACE) reveal that a series of jets and small eruptions took place there during the formation of the prominence. Plasma in each jet originated from a single site of flux cancellation and moved in opposite directions at a transverse speed of 80-250 km s-1 across the plane of the sky. Plasma eruptions showing complex morphology and dynamics started from two or more sites of flux cancellation and appear to have the same physical origin as the jets. The two filter ratio technique indicates that the EUV-emitting plasma in the jets and eruptions have transition-region temperatures of (2-3) × 105 K. It is also found from emission-measure analysis that the electron density is (0.7-1.9) × 1010 cm-3 and that each jet carries plasma mass of (1.7-4.6) × 1013 g and each eruption carries additional mass of (9-25) × 1013 g. Our results are consistent with the current pictures that (1) flux cancellation observed in the photosphere is a consequence of magnetic reconnection occurring in the chromosphere and (2) that a series of such magnetic reconnection events is able to supply the mass necessary for the formation of a solar prominence.