Emission lines of Fe XI in the 257-407 A wavelength region observed in solar spectra from EIS/Hinode and SERTS

F. P. Keenan, R. O. Milligan, D. B. Jess, K. M. Aggarwal, M. Mathioudakis, R. J. Thomas, J. W. Brosius, J. M. Davila

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1 Citation (Scopus)

Abstract

Theoretical emission-line ratios involving Fe xi transitions in the 257-407 A wavelength range are derived using fully relativistic calculations of radiative rates and electron impact excitation cross-sections. These are subsequently compared with both long wavelength channel Extreme-Ultraviolet Imaging Spectrometer (EIS) spectra from the Hinode satellite (covering 245-291 A) and first-order observations (similar to 235-449 A) obtained by the Solar Extreme-ultraviolet Research Telescope and Spectrograph (SERTS). The 266.39, 266.60 and 276.36 A lines of Fe xi are detected in two EIS spectra, confirming earlier identifications of these features, and 276.36 A is found to provide an electron density (N-e) diagnostic when ratioed against the 257.55 A transition. Agreement between theory and observation is found to be generally good for the SERTS data sets, with discrepancies normally being due to known line blends, while the 257.55 A feature is detected for the first time in SERTS spectra. The most useful Fe xi electron density diagnostic is found to be the 308.54/352.67 intensity ratio, which varies by a factor of 8.4 between N-e = 108 and 1011 cm-3, while showing little temperature sensitivity. However, the 349.04/352.67 ratio potentially provides a superior diagnostic, as it involves lines which are closer in wavelength, and varies by a factor of 14.7 between N-e = 108 and 1011 cm-3. Unfortunately, the 349.04 A line is relatively weak, and also blended with the second-order Fe x 174.52 A feature, unless the first-order instrument response is enhanced.
Original languageEnglish
Pages (from-to)1617-1624
JournalMonthly Notices of the Royal Astronomical Society
Volume404
Issue number3
Early online date21 May 2010
DOIs
Publication statusPublished - 2010

Keywords

  • atomic data
  • Sun: activity
  • Sun: corona
  • Sun: UV radiation
  • Astrophysics - Solar and Stellar Astrophysics

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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