Examination of the influence of streamer growth criteria on morphology

Work by Fowler, Daveny, and Hagedom showed that the morphology of an anode streamer could be modeled as stochastic growth of a branching fractal tree in point-plane geometry. In their work, the experimentally observed range of fractal densities, from sparse to bushy, was modeled by using two assumptions. One was that the growth was driven by Eⁿ, where E is the local electric field and n is 1, 2, 3, or 4. The other assumption is that there was a threshold (cutoff) electric field strength for streamer growth in a particular direction. This investigation first reproduced the results of the earlier study to demonstrate that the model and its software implementation yielded the previous results. The model was then modified to operate under a different set of assumptions. In this case, only linear electric field dependence was assumed, and the number density of available electrons was used as a parameter to match the observed data. In addition, rather than assume a sharp cutoff of the threshold field strength, the cutoff was assumed to be a function of electron density. Under these assumptions, it was also possible to simulate the experimentally observed behavior of anode streamers. The current assumptions are consistent with those that have proven to be useful in an earlier investigation.