The study of the dynamic process of umbral flashes

A detailed analysis has been made of Umbral Flashes in two sunspots. The results are as follows: the dynamic process of UF operates throughout the entire layer of formation of the H and K CaII line central reversals. The shape of the H and K line profile depends on the position of a sunspot on the solar disk. The parameters of the oscillatory process, i.e. the amplitude and the phase relations, are also dependent on the sunspot's position. An attempt to interpret the results led the authors to conclude an intrinsic relationship among the UF phenomenon, fine structure elements of the umbra at the photospheric level, and the rope-like configuration of the sunspot magnetic field. (author)