Spectroscopy of solar prominences from space and ground

Abstract

Two quiescent solar prominences were observed in July 2000 from SUMER aboard SOHO and from the two German solar telescopes at Tenerife. Two-dimensional images taken at the VTT simultaneously in the spectral lines Hbeta at 4862 Angstrom and Ca II at 8542 Angstrom show no significant spatial variation of their pressure-sensitive emission ratio. Slit spectra of the Ca II 8542 Angstrom and He I 10830 Angstrom lines obtained at the Gregory-Coude telescope yield 8000 K < T-kin < 9000 K and 3 km/s < Vn-th < 8 km/s. Among the various spectral ranges observed with SUMER, we first investigate the Lyman emission lines, which were fitted by Gaussians yielding reliable spectral radiances and line widths for the series members 5 < k < 18. A determination of the level population gives for the lower series members a Boltzmann temperature of 60 000 K, the higher members being over-populated. This temperature indicates an origin of the Lyman lines from hot surroundings of the cool prominence body seen in the ground-based data; this also holds for the 'hotter' SUMER lines.