Chromospheric network properties on short time scales from PSPT images

Three sequences of Ca II K images obtained on May 3, May 19 and June 7, 1997 with the PSPT (Precision Solar Photometric Telescope) instrument at the Rome Observatory have been used to study variations of the chromospheric network on a short time scale. We have applied to each PSPT image an automated algorithm developed to derive the skeleton representative of the network pattern and to identify the internetwork cells. By using both of them, we have computed power spectra of chromospheric intensity oscillations in network and in-ternetwork regions. We have also compared network cell patterns derived for a quiet region over two hours of observations and described the displacements of the barycenters of the cells bordered by the network loops. The spectral analysis on data obtained by applying the network identi-cation procedure shows distinct network and the internetwork intensity oscillations. We connrm the ndings of other workers that the network does not partecipate in chromospheric three-minute oscillations, but that instead it oscillates in slow wave motions which are neither present in the surrounding internetwork chromosphere.