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Session 1 - Chromosphere, Corona, Flares.
Display session, Friday, June 27
Ballroom B, Chair: Charles Kankelborg

[1.12] Measuring the He I/H ratio in a prominence using Lyman absorption

T. A. Kucera (ARC, NASA/GSFC), V. Andretta (NRC, NASA/GSFC), A. I. Poland (NASA/GSFC)

We investigate a method for measuring the ratio of neutral helium to hydrogen in solar prominences. The upper limit to the Lyman continuum occurs at 911 Åfor H, 504 Åfor He I, and 228 Åfor He II. Lyman absorption by prominences and other structures is clearly visible in emission of hot coronal lines observed by the Coronal Diagnostic Spectrometer (CDS) and Extreme Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). By comparing the absorption in lines absorbed by H only and by H and He I, the ratio of He I to H in prominences can be determined. We attempt to do this by comparing the absorption by a prominence in the Mg X line at 624.9 Åand the Mg IX line at 368.1 Åboth observed by CDS.

Program listing for Friday