Abstract
The optical depth at the head of the Lyman continuum, τ H, is determined at a number of positions in three hedgerow prominences using spectroheliograms (5″ × 5″ resolution) of C IIIλ 977, LC λ896, and O IV λ554 observed with the Harvard experiment on Skylab. At heights greater than 10″ above the limb the maximum value of τ H is 30 to 50, which occurs at the central part of the prominences. For one of the prominences the determination of τ H is found to be consistent with data from spectroheliograms of Mg X λ625. The degree of ionization of hydrogen is estimated from the intensity of LC λ896 at τ H ≫ 1. In the central part of a model prominence N P/N HI≤1.9 for a reasonable range of the electron densities, where N P and N HI are the proton density and the neutral hydrogen density, respectively.
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Kanno, M., Withbroe, G.L. & Noyes, R.W. Analysis of extreme-ultraviolet spectroheliograms of solar prominences. Sol Phys 69, 313–326 (1981). https://doi.org/10.1007/BF00149997
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DOI: https://doi.org/10.1007/BF00149997