Comparison of collisional-radiative model and average ion model of plasma kinetics in the non-local case

Two approaches to the development of a simplified model of non-equilibrium plasma kinetics have been discussed: chemical and solid-state ones. Within Bohr's ion model and Bohr's collisional-radiative model (BCRM) kinetics, the validity conditions of these two approaches are analysed based on ionic and configuration presentations of the initial approximation. The derivation of Bohr's average ion model (AIM) from BCRM and an analysis of the approximation accuracy in local thermodynamic equilibrium and coronal limits are given. The hydrogen-like Slater's AIM has I,een described. Plasma emission for two cases of the kinetics are calculated for non-LTE and LTE conditions, when radiative and collisional processes within K-and L-shells are dominant. The comparison of radiation spectra shows that for both the large and small optical thickness cases, the accuracy of the CRM approximation is close to that of the SAIM. The main contribution to the error of the average ion approximation is due to the coarse treatment of the line radiation transfer. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.