Emission lines of Fe x in active region spectra obtained with the Solar Extreme‐ultraviolet Research Telescope and Spectrograph

Department of Physics, The Catholic University of America, Washington, DC 20064, USA
Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 09/2008; 389(2):939 - 948. DOI: 10.1111/j.1365-2966.2008.13615.x
Source: arXiv

ABSTRACT Fully relativistic calculations of radiative rates and electron impact excitation cross-sections for Fe x are used to derive theoretical emission-line ratios involving transitions in the 174–366 Å wavelength range. A comparison of these with solar active region observations obtained during the 1989 and 1995 flights of the Solar Extreme-ultraviolet Research Telescope and Spectrograph (SERTS) reveals generally very good agreement between theory and experiment. Several Fe x emission features are detected for the first time in SERTS spectra, while the 3s23p5 2P3/2--3s23p4(1S)3d 2D3/2 transition at 195.32 Å is identified for the first time (to our knowledge) in an astronomical source. The most useful Fe x electron density (Ne) diagnostic line ratios are assessed to be 175.27/174.53 and 175.27/177.24, which both involve lines close in wavelength and free from blends, vary by factors of 13 between Ne= 108 and 1011 cm−3, and yet show little temperature sensitivity. Should these lines not be available, then the 257.25/345.74 ratio may be employed to determine Ne, although this requires an accurate evaluation of the instrument intensity calibration over a relatively large wavelength range. However, if the weak 324.73 Å line of Fe x is reliably detected, the use of 324.73/345.74 or 257.25/324.73 is recommended over 257.25/345.74. Electron densities deduced from 175.27/174.53 and 175.27/177.24 for the stars Procyon and α Cen, using observations from the Extreme-Ultraviolet Explorer (EUVE) satellite, are found to be consistent and in agreement with the values of Ne determined from other diagnostic ratios in the EUVE spectra. A comparison of several theoretical extreme-ultraviolet Fe x line ratios with experimental values for a θ-pinch, for which the plasma parameters have been independently determined, reveals reasonable agreement between theory and observation, providing some independent support for the accuracy of the adopted atomic data.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Semi-relativistic calculations are performed for the photoionization of Fe X (an important coronal ion) from its ground state 3s23p $^{5}(^{2}P^{0}_{3/2})$ and the first two excited states 3s23p $^{5}(^{2}P^{0}_{1/2})$ and 3s3p $^{6}(^{2}S_{1/2})$ using the Breit–Pauli R-matrix method. A lowest 41 state eigenfunction expansion for Fe XI is employed to ensure an extensive treatment of auto ionizing resonances that affect the effective cross-sections. In the present calculations, we have considered all the important physical effects like channel coupling, exchange and short range correlation. The present calculations using the lowest 41 target levels of Fe XI in the LSJ coupling scheme are reported and we expect that the present results should enable more accurate modelling of the emission spectrum of highly excited plasma from the optical to the far UV region.
    Journal of Astrophysics and Astronomy 33(3). · 0.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A detailed study of emission lines from Fe VII, Fe VIII, and Fe IX observed by the EUV Imaging Spectrometer on board the Hinode satellite is presented. Spectra in the ranges 170-212 Å and 246-292 Å show strongly enhanced lines from the upper solar transition region (temperatures 5.4
    The Astrophysical Journal 12/2009; 707(1):173-192. · 6.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Theoretical emission-line ratios involving FeXI transitions in the 257-407Å 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 245-291Å) and first-order observations (~235-449Å) obtained by the Solar Extreme-ultraviolet Research Telescope and Spectrograph (SERTS). The 266.39, 266.60 and 276.36Å lines of FeXI are detected in two EIS spectra, confirming earlier identifications of these features, and 276.36Å is found to provide an electron density (Ne) diagnostic when ratioed against the 257.55Å 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 257.55Å feature is detected for the first time in SERTS spectra. The most useful FeXI electron density diagnostic is found to be the 308.54/352.67 intensity ratio, which varies by a factor of 8.4 between Ne = 108 and 1011cm-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 Ne = 108 and 1011cm-3. Unfortunately, the 349.04Å line is relatively weak, and also blended with the second-order FeX 174.52Å feature, unless the first-order instrument response is enhanced.
    Monthly Notices of the Royal Astronomical Society 03/2010; 404:1617-1624. · 5.23 Impact Factor

Full-text (2 Sources)

Available from
May 20, 2014