To study the relative abundances of hydrogen and helium in prominences and find trends in its spatial distribution and variability over time by measuring the continuum absorption due to photoionization for EUV observations (e.g. JOP63, ref:Kucera98, ref:Gilbert05) and the absorption in H-alpha (6563 A) and He I (10830 A).
This study is primarily motivated by our findings from analyzing absorption due to filaments in H-alpha and He I MLSO observations (ref:Gilbert07). The results of that study and the preliminary results of our current, ongoing analysis of continuum absorption in archived EUV data from CDS, EIT, and TRACE show similar trends: stable (i.e. relatively unchanging) prominences have a relative helium surplus (compared to the average ratio of He to H) in the lower part and a relative helium deficit in the upper part, while more variable prominences (including those that are pre-eruption) have a homogenized spatial distribution of helium relative to hydrogen.
Further study needs to be done to find the scale heights of the H and He distribution and the time scales over which they change, but the ability to study more highly varying material requires co-temporal observations with better cadence and spatial resolution (via the newer observatories) than is currently available in the archived data of CDS, EIT, and TRACE. Note that coordinated observations are necessary to compare the simultaneous distributions of H0, He0, and He+.
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