KINETICS OF IONIZATION-RECOMBINATION OF A PLASMA AND POPULATION-DENSITY OF EXCITED IONS .1. EQUILIBRIUM PLASMA

It is shown that ions in a low-density plasma has an excited-state population density described by corona equilibrium or by the capture-cascade scheme; for hydrogen-like ions both have the same p-dependence (p is the principal quantum number) of n (p)/g (p)∝p-0.5 (n(p)/g(p) is the population density per unit statistical weight) for an optically thin high-temperature plasma. For an equilibrium condition, relative contribution is about 10: 1, verifying the corona model commonly assumed. For a low-temperature equilibrium plasma, however, the capture-cascade component dominates over the corona one for high-lying levels. In the high-density limit partial LTE holds only if the plasma is in ionization equilibrium or in complete LTE. In view of the fact that the equilibrium plasma is a rather exceptional case in actual situations, the theory is generalized: a plasma is decomposed into purely-ionizing- and purely-recombining-plasma components. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.