Moving Striations in Direct Current Glow Discharges

Abstract

A theoretical examination of the ion balance equations for a plasma, such as the positive column of a direct current glow discharge might be, shows that a uniform plasma is not always possible. When ionization proceeds by a two-stage process involving accumulated metastable excited atoms, as may be the case in the noble gases, small perturbations of the ion concentrations from their equilibrium values may not remain small. Under such conditions, a spatially uniform steady plasma cannot exist. A general stability criterion is developed which may be used whenever accurate expressions are known for the ion and metastable production and loss rate terms. Application of the stability criterion is made using several approximations.