On the stability of concentric spherical clouds of bipolar gaseous ions

It has been established by experimental measurement and by theory that long-lasting equal but oppositely charged distributions of positive and negative ions exist in the environment, particularly near operational high-voltage equipment. This paper considers the fundamentals of the geometric stability and deformations of these ionic clouds when they are exposed to stray electric fields. A simple, spherically symmetric model is put forward, and the analysis reveals characteristics that relate to the general behaviour of these bipolar clouds for all physical configurations. Charge drift methods are used in this analysis and there are technical mathematical difficulties even in this simple case which have been resolved to give a complete solution. Internal domains are identified whose boundary movements characterize the perturbation response of all ionic clouds. Time constants (half-lives) are found for the charge density changes within these domains which are inversely proportional to the product of the initial density and the mobility value. For perturbations that do not entirely separate the distributions, the final state, in general, is a largely undisturbed core surrounded by a mantle of radially decreasing charge density. The main findings on the geometric stability properties of these bipolar clouds are listed in the conclusions.