SOHO OBSERVATIONS OF THE CONNECTION BETWEEN LINE-PROFILE PARAMETERS IN ACTIVE AND QUIET REGIONS AND THE NET RED-SHIFT IN EUV EMISSION-LINES

We present high spatial and spectral resolution observations of one ac tive and one quiet-Sun region, obtained with CDS and SUMER on SOHO. Th e connections between the line profile parameters are studied and a sy stematic wavelength shift towards the red with increasing peak line in tensity (line broadening) is detected. The large scatter in the data c alls for another approach. We apply conditional probability analysis t o a series of EUV emission lines and find significant correlations bet ween line profile parameters. For a given interval in wavelength shift we find that: (1) line profiles with large intensities (line widths) and red shifts above the average constitute an increasing fraction of the profiles as the relative wavelength shift increases, (2) line prof iles with large intensities (line widths) and blue shifts compared to the average, on the other hand, constitute a decreasing fraction of th e profiles as the relative wavelength shift increases. These results e xtend the findings of an earlier quiet-Sun study from one to several e mission lines and expand the validity to include the active region. In terestingly, the active region observations show correlations between peak line intensity and wavelength shift in the coronal lines. The ten dency for red-shifted profiles to be more intense than blue-shifted pr ofiles will shift line profiles derived by integrating along the slit towards the red. From the present observations we are not able to dete rmine the fraction of the net red shift that emerges from this correla tion. We suggest that the same mechanism is responsible both for the c orrelation between the line profile parameters and for the differentia l red shift between the transition region and chromospheric emission l ines.