The Ultraviolet Resonance Lines of Neutral Helium from the Sun
Open Access
- 1 January 1969
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 142 (1) , 53-70
- https://doi.org/10.1093/mnras/142.1.53
Abstract
The population densities of the bound levels of neutral helium have been calculated for a 41-level model atom using recent calculations of the cross-sections for collisional excitation from the 23S level to the singlet levels, some of which are significant. The effect of optical thickness in the resonance lines is included and the calculation used in an interpretation of the measured intensities of the lines at 584 and 537 Å emitted by the Sun. These two intensities may be used to determine the optical thickness and electron temperature of the emitting layer for an assumed electron density. The electron temperatures obtained lie between 30 000 and 45 000°K. Additional observations are necessary to determine the electron density; two suggestions are made.Keywords
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