Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1976
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976apj...203..509l&link_type=abstract
Astrophysical Journal, vol. 203, Jan. 15, 1976, pt. 1, p. 509-520.
Astronomy and Astrophysics
Astrophysics
24
Continuous Spectra, Helium Ions, Lyman Spectra, Solar Spectra, Ultraviolet Spectroscopy, Atomic Collisions, Line Spectra, Oso-7, Photoionization, Solar Corona, Solar Flares, Solar Flux, Solar Prominences, Tables (Data)
Scientific paper
OSO-7 observations of the first five Lyman lines and the Lyman continuum of He II are given for the quiet sun, a coronal hole, prominences, filaments, and the flare of August 7, 1972. These data are calibrated and given in specific intensity units together with color and brightness temperatures for the He II continuum. It is found that He II is overionized in all features except the flare and that the continuum is formed at temperatures near 14,000 K. The He II-He III ionization equilibrium appears to be dominated by photoionizations and radiative recombinations. Schematic calculations for realistic chromosphere and transition-region models can account for the observed intensities of Ly-beta through Ly-epsilon, the Lyman continuum, and its color temperature. To account for the intensity of Ly-alpha, either an implausible 100-km plateau at temperatures near 80,000 K is needed or, more likely, the diffusion-enhanced collisional excitation should be incorporated into the models.
Chapman Robert Dewitt
Glackin David L.
Linsky Jeffrey L.
Neupert Werner M.
Thomas Robert J.
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