Influence of the Electric Fields of Thunderstorms on Radon-222 Daughter Ion Concentrations
Some of the 222Rn daughters present in the atmosphere are known to exist as positive ions having mobilities in the range of ordinary atmospheric small ions. Previous work has shown that the concentration of these ions near the ground decreases markedly in the presence of thunderstorms although the concentration of the parent 222Rn remains essentially unchanged. In this paper the nature of this effect is examined in terms of ion migration due to electric fields, attachment to condensation nuclei, and recombination effects. Data from 40 thunderstorms studied at the Langmuir laboratory clearly show that the depletion of the radon daughter ions as well as the ordinary atmospheric small ions of positive charge near ground level is due primarily to ion migration under the influence of storm-produced electric fields. However, attachment processes become important for condensation nucleus concentrations in excess of about four times normal values. Recombination appears to play only a minor role. The experimental data are supported by a one-dimensional time-dependent numerical model developed by Roffman in our laboratory which includes terms for ion attachment and recombination, electric field, eddy diffusion, and vertical wind.
KeywordsEddy Diffusion Condensation Nucleus Local Standard Time Fair Weather Field Reversal
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