Time dependence of the chromospheric network properties

Continuous sets of white-light and Ca II K-line images are used to derive optimal proxy indices of the solar irradiance variation. In the framework of the RISE (Radiative Inputs of the Sun to Earth) project the first PSPT (Precise Solar Photometric Telescope) telescope is operative at the Monte Mario Observatory in Rome since February 1996. A sequence of PSPT Ca K-line images obtained in a period of minimum solar activity (from July to November 1996) have been used to analyze the time dependence of the intensity, the morphology and the scaling properties of the network cells.