EUV SPECTROSCOPY OF THE SUNSPOT REGION NOAA-7981 USING SOHO I - LINE EMISSION AND TUNE DEPENDENCE

EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981, were obtained on 2 August 1996 with the Coronal Diagnostic Spectromete r (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation (S UMER) on the Solar and Heliospheric Observatory (SOHO). The spectral l ines formed in the transition region and corona show considerable stru cture and large deviations from a uniform spatial distribution over th e active region. Enhanced EUV emissions in transition region lines are concentrated in small regions outside the umbra of the sunspot throug hout most of the observing sequence. Only during a short, active perio d do we find an enhanced line emission that reaches into the umbra. Pr eliminary values for the umbral intensity are given. Marked changes ar e detected between the spatial distribution of line emission in the tr ansition region and the low corona. The difference is not limited to c ool and hot non-flaring loops not being cospatial, but includes differ ences both regarding the time variability and the orientation and size of the emission features. Whereas both rapid (approximate to 4 and 2 min) and slow (approximate to 10 and 12 h) temporal variations are fou nd in the chromosphere (He I 584 Angstrom) and transition region (O V 629 Angstrom), the response in the low corona (Mg IX 368 Angstrom) is slow (approximate to 5 h). Furthermore, marked differences between the spatial distributions in the Mg VIII 315 Angstrom, Mg IX 368 Angstrom lines formed in the low corona and the coronal Fe XIV 334 Angstrom, F e XVI 360 Angstrom lines are detected.