SUMER observations detecting downward propagating waves in the solar transition region

The O IV density sensitive emission lines around 1400 A, using the solar ultraviolet measurement of emitted radiation (SUMER) instrument onboard the Solar and Heliospheric Observatory (SOHO), are reported on. The data for the quiet sun, obtained close to the disk center and the solar limb were acquired. A systematic correlation between a density sensitive emission line ratio and Doppler shift across the same emission profiles was obtained. The correlation is such that the density is higher in the downflowing than in the upflowing plasma. The results are in good agreement with the simulations of downward propagating waves.