CDS observations of the connection between line intensity and Doppler shift in the active region NOAA 7981

Although CDS was primarily constructed to observe the intensities of several lines simultaneously, we find that the relative line-of-sight velocity may be determined with an accuracy of 5 km s(-1) or better for the stronger lines. We study the connection between the line intensity and the wavelength shift for a series of emission Lines in a medium size sunspot and its surroundings. Consider first the transition region Lines. We find that line profiles from O IV 554 Angstrom and O V 629 Angstrom, with large intensities and with redshifts in excess of the average, constitute an increasing fraction of the number of profiles in a given velocity interval as the relative Doppler velocity increases. On the other hand, line profiles with large intensities and blueshifts compared to the average constitute a decreasing fraction of the number of profiles in a given velocity interval with increasing relative velocity. Interestingly, the coronal lines Mg IX 368 Angstrom and Fe XVI 360 Angstrom show differences between profiles that are redshifted and blueshifted relative to the average for relative velocities in the range 5 - 20 km s(-1), indicating that the net redshift phenomenon may extend into the corona.