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Mg I absorption features in the solar spectrum near 9 and 12 micronsHigh-resolution FTS observations from the Kitt Peak National Solar Observatory and the Spacelab 3 ATMOS experiment have revealed additional infrared transitions due to Mg I in the spectra of both quiet sun and sunspot penumbra. In contrast to previous observations, these transitions are seen in absorption, not emission. Absorption intensities range from 1 to 7 percent of the continuum in the quiet sun. In the penumbra, the same features appear to show Zeeman splitting. Modeling of the line profiles in the photospheric spectrum shows evidence for a factor of three overabundance in the n = 5 or more levels of Mg I in the upper photosphere, but with no deviations from a Planck source function. It is concluded that whatever the process that produces the emission (including the Lemke and Holweger mechanism), it must occur well above the tau(5000) = 0.01 level.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Glenar, David A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Reuter, Dennis C. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Deming, Drake (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Chang, Edward S. (Massachusetts, University Amherst, United States)
Date Acquired
August 14, 2013
Publication Date
December 1, 1988
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 335
ISSN: 0004-637X
Subject Category
Distribution Limits