Downward propagating waves detected in the chromospheric network by SOHO/CDS.

We analyze temporal variations in the intensities and the Doppler shifts of the He I 584.33 A (chromosphere) and O V 629.73 A (transition region) spectral lines measured in chromospheric network near disk center with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory SOHO). Wavelet power analysis gives evidence of intermittent chromospheric and transition region oscillations with periodicities in the 250 - 450 s range. Wavelet phase difference analysis shows relevant negative phase delay of -20 degrees which corresponds to the time shift of -17 s between oscillations of the He I and O V intensities with periodicity around 300 s. On the other hand no significant phase delays are found between oscillations of the Doppler shifts of these spectral lines. We interpret these results as giving evidence of compressive waves that propagate downward from the transition region to the chromosphere in the particular chromospheric network.