EUV plasma diagnostics for nitrogen-like ions from spectra obtained by SUMER/SOHO

Abstract

We discuss the potential for plasma diagnostics of forbidden transitions from the ground levels in the nitrogen-like ions: Al VII, Si VIII, P DC, S X, Ar XII, K XIII and Ca XIV. These transitions fall in the UV spectral range and have been recently observed by the SOHO/SUMER instrument in the solar spectrum. Some of the lines used in the present study have been measured by SUMER for the first time: higher resolution and sensitivity allow for the identification and measurement of weaker lines than previously, at positions higher off the solar limb. We show that current atomic data are still not able to reproduce the observations and that further work is required to solve inconsistencies between observations and theoretical predictions.