Paola Testa, Jeremy J. Drake, Enrico Landi
The Atmospheric Imaging Assembly (AIA) and the Exteme-ultraviolet Variability
Experiment (EVE) onboard the Solar Dynamics Observatory include spectral
windows in the X-ray/EUV band. Accuracy and completeness of the atomic data in
this wavelength range is essential for interpretation of the spectrum and
irradiance of the solar corona, and of SDO observations made with the AIA and
EVE instruments. Here we test the X-ray/EUV data in the CHIANTI database to
assess their completeness and accuracy in the SDO bands, with particular focus
on the 94A and 131A AIA passbands. Given the paucity of solar observations
adequate for this purpose, we use high-resolution X-ray spectra of the
low-activity solar-like corona of Procyon obtained with the Chandra Low Energy
Transmission Grating Spectrometer (LETGS). We find that while spectral models
overall can reproduce quite well the observed spectra in the soft X-ray range
ll < 50A, and at the EUV wavelengths ll >130A, they significantly underestimate
the observed flux in the 50-130A wavelength range. The model underestimates the
observed flux by a variable factor ranging from \approx 1.5, at short
wavelengths below \sim50A, up to \approx5-7 in the \sim 70-125A range. In the
AIA bands covered by LETGS, i.e. 94A and 131A, we find that the observed flux
can be underestimated by large factors (\sim 3 and \sim 1.9 respectively, for
the case of Procyon presented here). We discuss the consequences for analysis
of AIA data and possible empirical corrections to the AIA responses to model
more realistically the coronal emission in these passbands.
View original:
http://arxiv.org/abs/1110.4611
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