A self-consistent, two-dimensional hybrid fluid-particle model is presented and used to describe the electrical behavior of dc low-pressure discharges in the current range ${10}^{\mathrm{-}7}$–${10}^{\mathrm{-}2}$ A in argon for products of the gas pressure and the gap spacing (pd) from 1 to 3.3 cm torr. The two-dimensional distributions of the potential, charged particle densities and ionization source term at steady state are shown to illustrate the discharge behavior during the transition from the normal to the abnormal regimes. For the larger values of pd, a positive column region as well as the cathode regions are clearly apparent. The model used here consists of Poisson’s equation for the electric field coupled to the continuity equations for the electrons and ions with the important feature that the ionization source term appearing in the continuity equations is nonlocal and determined from a Monte Carlo simulation. This description yields a unified physical picture of discharge behavior in the cathode fall, negative glow, and positive column regions over a wide range of discharge currents.

• Received 12 November 1993

DOI:https://doi.org/10.1103/PhysRevE.49.5607