3D modelling of self-organized patterns of spots on anodes of DC glow discharge

TL;DR

This paper presents a self-consistent simulation of self-organized spot patterns on metallic anodes in DC glow discharges, revealing unexpected behaviors such as local current reversal and mini-cathode formation.

Contribution

It introduces a novel computational approach to model anode spot patterns, uncovering behaviors that challenge traditional self-organization theories in plasma physics.

Findings

Reversal of local anode current density within spots

Formation of mini-cathodes inside spots

Multiple stable solutions with and without spots

Abstract

Self-organized patterns of spots on a at metallic anode in a cylindrical glow dis- charge tube are simulated self-consistently. A standard model of a glow discharge is used, comprising conservation and transport equations for a single species of ion and electrons, written with the use of the drift-diffusion and local-field approximations, and the Poisson equation. The computation domain is the region from the anode to the discharge column; only processes in the near-anode region are considered. Multiple solutions, existing in the same range of discharge current and describing modes with and without anode spots, are computed by means of a stationary solver. The computed spots exhibited unexpected behavior. A reversal of the local anode current density in the middle of each of the spots was found, i.e. mini-cathodes are formed inside the spots. The solutions do not fit into the conventional pattern of self-organization in bistable nonlinear dissipative systems; e.g. the modes are not joined by bifurcations.