Emission lines of FeXI in the 257-407Å wavelength region observed in solar spectra from EIS/Hinode and SERTS
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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2010
- DOI:
- 10.1111/j.1365-2966.2010.16389.x
- arXiv:
- arXiv:1001.3627
- Bibcode:
- 2010MNRAS.404.1617K
- Keywords:
-
- atomic data;
- Sun: activity;
- Sun: corona;
- Sun: UV radiation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 9 pages, 5 figures, 13 tables