The EUV spectrum of the Sun: quiet and active Sun irradiances and chemical composition. (arXiv:1901.08841v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zanna_G/0/1/0/all/0/1">G. Del Zanna</a>
We benchmark new atomic data against a selection of irradiances obtained from
medium-resolution quiet Sun spectra in the EUV, from 60 to 1040 AA. We use as
a baseline the irradiances measured during solar minimum on 2008 April 14 by
the prototype (PEVE) of the Solar Dynamics Observatory Extreme ultraviolet
Variability Experiment (EVE). We take into account some inconsistencies in the
PEVE data, using flight EVE data and irradiances we obtained from Solar &
Heliospheric Observatory (SoHO) Coronal Diagnostics Spectrometer (CDS) data. We
perform a differential emission measure and find overall excellent agreement
(to within the accuracy of the observations, about 20%) between predicted and
measured irradiances in most cases, although we point out several problems with
the currently available ion charge state distributions. We used the
photospheric chemical abundances of Asplund et al. (2009). The new atomic data
are nearly complete in this spectral range, for medium-resolution irradiance
spectra. Finally, we use observations of the active Sun in 1969 to show that
also in that case the composition of the solar corona up to 1 MK is nearly
photospheric. Variations of a factor of 2 are present for higher-temperature
plasma, which is emitted within active regions.These results are in excellent
agreement with our previous findings.
We benchmark new atomic data against a selection of irradiances obtained from
medium-resolution quiet Sun spectra in the EUV, from 60 to 1040 AA. We use as
a baseline the irradiances measured during solar minimum on 2008 April 14 by
the prototype (PEVE) of the Solar Dynamics Observatory Extreme ultraviolet
Variability Experiment (EVE). We take into account some inconsistencies in the
PEVE data, using flight EVE data and irradiances we obtained from Solar &
Heliospheric Observatory (SoHO) Coronal Diagnostics Spectrometer (CDS) data. We
perform a differential emission measure and find overall excellent agreement
(to within the accuracy of the observations, about 20%) between predicted and
measured irradiances in most cases, although we point out several problems with
the currently available ion charge state distributions. We used the
photospheric chemical abundances of Asplund et al. (2009). The new atomic data
are nearly complete in this spectral range, for medium-resolution irradiance
spectra. Finally, we use observations of the active Sun in 1969 to show that
also in that case the composition of the solar corona up to 1 MK is nearly
photospheric. Variations of a factor of 2 are present for higher-temperature
plasma, which is emitted within active regions.These results are in excellent
agreement with our previous findings.
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