Atomic data for astrophysics: Fe x soft X-ray lines

Abstract

New atomic calculations for Fe x are presented. They focus on the need to model the soft X-ray spectrum and in particular the line at 94.0 Å which is the dominant contribution to the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 94 Å band in quiet Sun conditions. This line, and others in the band, are due to strong decays from n = 4 levels. We present new large-scale R-matrix (up to n = 4) and distorted-wave (DW, up to n = 6) scattering calculations for electron collisional excitation and compare them to earlier work. We find significant discrepancies with previous calculations. We show that resonances significantly increase the cross-sections for excitations from the ground state to some n = 4 levels, in particular to those in the 3s 2 3p 4 4s configuration. Cascading from higher levels is also important. We suggest a new identification for the 3s 3p 6 2 S 1/2 -3s 3p 5 4s 2 P 3/2 transition, that has a predicted intensity larger than the decays from the 3s 2 3p 4 4s levels which were identified by Edlén in 1936. The results presented here are relevant to our understanding of transitions from n = 4 levels in a wide range of other ions.

Atomic data for astrophysics: Fe xi soft X-ray lines

“…The importance of resonance effects for the n = 4 levels was found when calculating atomic data for Fe x (Del Zanna et al 2012b), but was also found in Fe xii (Del Zanna et al 2012a) and Fe xiii . Here, we present new large-scale scattering calculations for the Fe xi soft X-ray lines.…”

Signatures of the non-Maxwellianκ-distributions in optically thin line spectra

“…Liang et al 2009Liang et al , 2010Liang et al , 2012O'Dwyer et al 2012;Del Zanna et al 2010, 2012aDel Zanna 2011a,b;Del Zanna et al 2012b;, 2013Del Zanna et al 2014). These calculations represent significant improvements to previous atomic data, since they include a large number of levels and the associated cascading and resonances.…”

“…(4)) for each ion are also provided (Del Zanna et al 2014, 2012aDel Zanna & Storey 2013;Del Zanna et al 2010, 2012b). …”

“…For line identifications, see Del ), Del Zanna et al (2012a, and references therein. The Fe x ion has only a few density-sensitive line ratios that also show non-negligible sensitivity to T .…”

“…Significant progress has also been made on line identifications of complex coronal Fe ions (e.g. Del Zanna et al , 2014Del Zanna & Mason 2005;Young 2009;Del Zanna 2010, 2011a, 2012Del Zanna et al 2012a).…”