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J. M. Laming, U. Feldman (NRL)
The solar helium abundance measured in situ in the fast solar wind is typically 0.05 by number relative to hydrogen, whereas in the solar envelope it is measured by helioseismology to be 0.085. We report on analyses of spectra taken by SOHO/SUMER of solar polar coronal holes to determine the abundance of helium by emission line spectroscopy. In comparison with our earlier measurement in an equatorial streamer, coronal hole spectra are less intense, which makes determining the intensities of hydrogen lines to adequate precision much more difficult. Using other strong lines in the spectrum, e.g. C IV, N V, O VI we find helium abundance values more consistent with those in the fast solar wind than the photospheric value.
This work is supported by the NRL/ONR Solar Magnetism and the Earth's Environment 6.1 Research Option and by NASA Contract S137836.
The author(s) of this abstract have provided an email address for comments about the abstract: jlaming@ssd5.nrl.navy.mil