Emission lines of Fe XI in the 257-407 A wavelength region observed in solar spectra from EIS-Hinode and SERTS - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




Emission lines of Fe XI in the 257-407 A wavelength region observed in solar spectra from EIS-Hinode and SERTS - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Theoretical emission-line ratios involving Fe XI transitions in the 257-407 Awavelength range are derived using fully relativistic calculations of radiativerates and electron impact excitation cross sections. These are subsequentlycompared with both long wavelength channel Extreme-Ultraviolet ImagingSpectrometer EIS spectra from the Hinode satellite covering 245-291 A, andfirst-order observations 235-449 A obtained by the Solar Extreme-ultravioletResearch Telescope and Spectrograph SERTS. The 266.39, 266.60 and 276.36 Alines of Fe XI are detected in two EIS spectra, confirming earlieridentifications of these features, and 276.36 A is found to provide an electrondensity diagnostic when ratioed against the 257.55 A transition. Agreementbetween theory and observation is found to be generally good for the SERTS datasets, with discrepancies normally being due to known line blends, while the257.55 A feature is detected for the first time in SERTS spectra. The mostuseful Fe XI electron density diagnostic is found to be the 308.54-352.67intensity ratio, which varies by a factor of 8.4 between N e = 10^8 and 10^11cm^-3, while showing little temperature sensitivity. However, the 349.04-352.67ratio potentially provides a superior diagnostic, as it involves lines whichare closer in wavelength, and varies by a factor of 14.7 between N e = 10^8 and10^11 cm^-3. Unfortunately, the 349.04 A line is relatively weak, and alsoblended with the second-order Fe X 174.52 A feature, unless the first-orderinstrument response is enhanced.



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

Source: https://arxiv.org/







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