Title:
Benchmarking atomic data for astrophysics: Si iii
Authors:
Del Zanna, G.; Fernández-Menchero, L.; Badnell, N. R.
Affiliation:
AA(DAMTP, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 0WA, UK g.del-zanna@damtp.cam.ac.uk), AB(Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK), AC(Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK)
Publication:
Astronomy & Astrophysics, Volume 574, id.A99, 11 pp. (A&A Homepage)
Publication Date:
02/2015
Origin:
EDP Sciences
Astronomy Keywords:
atomic data, techniques: spectroscopic, Sun: corona, line: identification
DOI:
10.1051/0004-6361/201424394
Bibliographic Code:
2015A&A...574A..99D
Abstract
We investigate the main spectral diagnostics for Si iii UV lines, which have been previously used to measure electron densities, temperatures, and to suggest that non-Maxwellian electron distributions might be present in the low transition region of the solar atmosphere. Previous atomic calculations and observations are reviewed. We benchmark the observations using a new large-scale R-matrix scattering calculation for electron collisional excitation of Si iii, carried out with the intermediate-coupling frame transformation (ICFT) method. We find generally good agreement between predicted and observed line intensities, if one takes into account the different temperature sensitivity of the lines, and the structure of the solar transition region. We find no conclusive evidence for the presence of non-Maxwellian electron distributions.
The full dataset (energies, transition probabilities and rates) are available in electronic form at our APAP website (http://www.apap-network.org)