Abstract
The electrffication of growing ice crystals during condensation and evaporation was studied in ionized air of various small-ion concentrations. It was found that ice crystals were electrified positively during condensation and negatively during evaporation. Because of the difficulty of controlling humidity during evaporation, we worked quantitatively only on electrification during condensation. Forty percent more positive small ions than negative ones were caught preferentially on the growing surfaces of the ice crystals. This phenomenon is explained by the interaction of small ions and ice crystals through the negative surface potential of the ice, where the negative surface potential is caused by the negatively electrified dislocations at the ice surface. This positive electrification of ice crystals suggests that clouds consisting of the solid phase have excess positive space charge, in contrast with the author's recent finding of excess negative space charge of warm clouds.
