The Excitation of Several Iron and Calcium Lines in the Visible Spectrum of the Solar Corona

Abstract

New atomic data have been obtained for the coronal ions Fe X, Fe XI, Fe XIV, Ca XII, Ca XIII and Ca XV, using a computer package developed at University College, London. Energy levels and radiative transition probabilities have been computed allowing for configuration interaction and relativistic effects. The electron scattering problem has been solved using the ‘distorted wave’ approach. All radiative and collisional processes contributing to the equilibrium equations for the ground configuration were considered, including cascade via the excited configurations and the effect of autoionizing levels on the electron collisional excitation rate. Wherever possible, the accuracy of the atomic parameters has been estimated and the results compared to those of previous authors. The atomic data, level populations and emission rates for the ions studied, are tabulated for various physical conditions appropriate to the solar corona.