COMPARISON OF EXPLICIT AND EFFECTIVE MODELS FOR CALCULATING IONIC POPULATIONS IN ARGON PLASMAS

Calculations have been performed to model the state populations of arg on plasmas at electron densities at and above those required for the v alidity of coronal equilibrium. Both effective and explicit models hav e been used, and both are based on the same set of atomic cross sectio ns. The effective model includes ground and singly excited states expl icitly, while the effect of autoionizing states is accounted for by br anching factors which describe their depopulation into the various non -autoionizing states. The explicit model considers both autoionizing a nd non-autoionizing states explicitly. The effective model requires a significantly reduced amount of computer time and memory. Good agreeme nt between the two models can be obtained through moderate densities i f the branching factors include electron density dependent terms which describe the collisional stabilization of each autoionizing state. Th e effective model breaks down as density is increased because the popu lation of individual autoionizing states become significant. Results f or both ionization balance and radiated power loss are presented.