Astronomy and Astrophysics – Astronomy
Scientific paper
May 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...426..414l&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 426, no. 1, p. 414-424
Astronomy and Astrophysics
Astronomy
13
Abundance, Helium, Magnetohydrodynamic Flow, Radiative Heat Transfer, Red Shift, Sunspots, Ultraviolet Astronomy, Ultraviolet Spectra, Carbon, Hydrogen, Ionization, Nitrogen, Rocket-Borne Instruments, Solar Temperature, Ultraviolet Spectrometers, Ultraviolet Telescopes
Scientific paper
The ultraviolet spectrum of a redshifted plasma flow appearing over a sunspot in data obtained during the Naval Research Laboratory (NRL) High Resolution Telescope and Spectrograph (HRTS I) flight is interpreted as a radiatively cooling plasma. For most lines emitted from this plasma, the assumption of ionization equilibrium during the cooling is good; however, for He II this is not the case. In order to get the helium abundance by comparison with other lines, one must integrate differential equations for the various He ionization fractions, and the temperature, and then calculate the radiation emitted. Our result for the solar helium abundance is in the range 0.078-0.22 relative to hydrogen, with the uncertainty arising from lack of knowledge of model parameters.
Feldman Uri
Laming Martin J.
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