Ion Cloud Modeling

Abstract

Abstract : New quantitative procedures are developed for describing the deposition ion of clouds from high-altitude barium releases. The early-time expansion of the neutral vapor cloud via a snowplow model with diffusion added is developed. The inclusion of diffusion provides a description of the evolution of the neutral cloud into a Gaussian shape and provides the basis for a plausible explanation of why the apparent large size of photographic images of early-time expanding neutral clouds are larger than can be explained by the release of reasonable amounts of neutral vapor. The subsequent deposition of ionization in the expanding neutral cloud results in an ion cloud that is substantially narrower than the neutral cloud consistent with a number of radar measurements. The influence of neutral winds and settling under gravity on the distribution of ionization along magnetic field lines and the descent through the atmosphere is treated analytically. It is shown that downward winds can delay the decrease in the peak ion concentration and that altitude-dependent winds are more effective in limiting the increase in length of the ion cloud.