Properties of brightenings seen in CDS movies

We discuss movies obtained with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO) and recorded at a cadence of 30 seconds during 4 hours in a quiet sun region. These movies are used to investigate brightness variations of solar features at different levels in the solar atmosphere. We employ histograms and scatter-plot diagrams in order to gain a "statistical" view of these variations. Preliminary results are presented. We find significant variability at all time scales in all parts of the quiet Sun, from darkest intranetwork to brightest network. Such variations are observed in the chromospheric He I line, the transition region O V and coronal Mg IX lines. For the first 2 lines the relative variability is independent of brightness, while for the coronal line it increases somewhat with brightness. Finally, most of the variability appears to take place on time scales longer than 5 minutes for all 3 spectral lines.