Emergence of sheared magnetic flux tubes in an active region observed withthe SVST and TRACE

The active region NOAA AR 8331 was a target of an international ground-base d observational campaign in the Canaries and coordinated with space instrum ents (TRACE and Yohkoh). We focus our study on observations obtained with t he SVST at LaPalma, and with TRACE. On 10 September 1998, arch-filament sys tems were observed with high spatial and temporal resolution, from the lowe r to the upper atmosphere of the Sun, during five hours. Flux tubes emerged with increasing shear, which apparently led to energy release and heating in the overlying corona. A model for filament formation by the emergence of U-shaped loops from the subphotosphere, as proposed by Rust and Kumar (199 4), is supported by the present observations. The coronal response to these events is visualized by rising, medium-scale loop brightenings. The low-ly ing X-ray loops show short-lived, bright knots which are thought to result from interaction between different loop systems.