On the global model approximation

Global models are commonly employed to study chemically complex low temperature, low-pressure plasma discharges. However, due in part to the inherent non-uniformity of charged species density in confined plasmas, these models are often regarded as crude first-order approximations. This view is supported by the literature, where global models typically give only broad qualitative agreement when compared with experimental measurements. Recently, the present authors have argued against such comparisons being a useful indicator of the validity of the underlying model assumptions. Choosing instead to quantify the validity of a relatively simple global model by comparing it with a one-dimensional particle-in-cell simulation, they found the two treatments to be in quite good agreement over an extended region of parameter space. This paper is an attempt to offer further insight into this result.