[Loops] paper on assessment of atomic data for SDO analyses

[Paola Testa]

Dear all,

here is a link to another paper, accepted for publication on ApJ, presenting
an analysis of Chandra high-resolution stellar spectra to test the 
accuracy and
completeness of the atomic data of CHIANTI 6 for SDO analyses

http://adsabs.harvard.edu/abs/2011arXiv1110.4611T

cheers,
Paola


"Testing EUV/X-ray Atomic Data for the Solar Dynamics Observatory"
Paola Testa, Jeremy J. Drake, Enrico Landi

ABSTRACT
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 <~ 50A, and at the EUV wavelengths >~ 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 ~1.5, at short 
wavelengths below ~50A, up to ~5-7 in the ~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 (~3 and ~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.