Journal
ASTRONOMY & ASTROPHYSICS
Volume 565, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201423471
Keywords
Sun: abundances; Sun: corona; Sun: X-rays, gamma rays; techniques: spectroscopic
Categories
Funding
- STEC (UK) through the University of Cambridge DAMTP
- Science and Technology Facilities Council [PP/E004857/2, ST/J001570/1, ST/L000636/1] Funding Source: researchfish
- UK Space Agency [ST/J001732/1] Funding Source: researchfish
- STFC [PP/E004857/2, ST/J001570/1, ST/L000636/1] Funding Source: UKRI
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A brief review of studies of elemental abundances and emission measures in quiescent solar active region cores is presented. Hinode EUV Imaging Spectrometer (EIS) observations of strong iron spectral lines have shown sharply peaked distributions around 3 MK. EIS observations of lines emitted by a range of elements have allowed good estimates of abundances relative to iron. Ilowever, X-ray observations are required to measure the plasma emission above 3 MK and the abundances of oxygen and neon. We revisit, using up-to-date atomic data, older X-ray observations obtained by a sounding rocket and by the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2, compared to the photospheric values. Similar results are obtained from FCS observations of six quiescent active region cores. The FCS observations also indicate that the emission measure above 3 MK has a very steep negative slope, with very little plasma observed at 5 MK or above.
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