The solar XUV spectrum of He II

Journal Article · Thu Jan 15 04:00:00 EST 1976 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/154106· OSTI ID:7354743

Linsky, J L; Glackin, D L; Chapman, R D; Neupert, W M; Thomas, R J

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 1972 August 7 flare. These data are calibrated and given in specific intensity units together with color and brightness temperatures for the He ii continuum. We find 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 L..beta..-Lepsilon, the Lyman continuum, and its color temperature. To account for the intensity of L..cap alpha.., either an implausible 100 km plateau at temperatures near 80,000 K is needed or more likely, the incorporation of diffusion-enhanced collisional excitation into the models. (AIP)

• Research Organization: Joint Institute for Laboratory Astrophysics, National Bureau of Standards
• OSTI ID: 7354743
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 203:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHEMICAL COMPOSITION
CRYOGENIC FLUIDS
ELEMENTS
FLUIDS
HELIUM
IONIZATION
LYMAN LINES
NONMETALS
PHOTOIONIZATION
RARE GASES
RECOMBINATION
SOLAR ACTIVITY
SOLAR CORONA
SOLAR FLARES
SOLAR PROMINENCES
SPECTRA
STARS
SUN
ULTRAVIOLET SPECTRA