Time evolution of mottles observed in H_alpha

In April 2002, H_alpha observations of the solar chromosphere with high spatial and spectral resolution were obtained with the 'Göttingen Fabry-Perot Spectrometer' mounted in the Vacuum Tower Telescope (VTT) at the Observatory del Teide/Tenerife. In this work, we analyze a short time sequence of a quiet region with chains of mottles. Some physical parameters of dark mottles are determined by using Beckers' cloud model, which assumes that the source function, the Doppler width and the velocity are constant within the cloud along the line of sight. Here we discuss some morphological properties as well as temporal evolution of several physical parameters of individual mottles.