Astronomical Institute, Ondrejov, Czech Republic

We present the first results of numerical simulations of pulse beam heating of the chromosphere and TR during the impulsive phase of a flare. The electron beams are described by a particle code, while the atmospheric dynamics is treated by 1D hydrodynamical code. The ionization balance, radiation losses and formation of chromospheric lines is computed with time-dependent NLTE code based on MALI technique. Furthermore, we present an observing programme to detect the fast line-intensity variations relevant to a pulse-beam heating. Namely we show some preliminary results of H-alpha temporal variations detected by the Multichannel Flare Spectrograph (MFS) of the Ondrejov Observatory. This instrument allows the recording of fast line intensity/profile variations in 3 various lines (by means of a video CCD system) and will operate simultaneously with Czech hard X-ray photometer and with HESSI. Currently it participates in Max-Millenium campaigns.