Flare June 7, 2011, and analysis of eruptive prominence fragments

Solar flares can be accompanied by high plasma velocities exceeding several hundred km/s. Detection and measurement of such velocities is limited by narrow-band and small wavelength range in most solar instruments. However, similar events with Doppler velocities exceeding two hundred km/s have been detected by the solar optical spectrographs at the Ondřejov Observatory. We present the results of the analysis of our multi-wavelength observations performed during the solar flare of June 7, 2011 and the calculation of several physical parameters of the eruptive prominence fragments following the flare. The calculation of the radiation of heated gas are performed taking into account self-absorption in the spectral lines of hydrogen and calcium. All the crucial processes of discrete level populating and depopulating are taken into account in the balance equations. The theoretical radiation fluxes in the lines coincide with those observed in the temperature range of 6300–10000 K at a gas concentration of about (3–5) × 10¹⁰ см^–3 , a gas layer thickness of 6800–7000 km and a column density of (2–4) × 10¹⁹ см^–2 .