The Growth and Fragmentation of Ice Crystals in an Electric Field

Abstract

Thousands of ice crystals are generated by placing an electrified wire in a supercooled cloud. The crystals result from the growth of fragile forms of ice on the wire, followed by fragmentation of these forms under the stress of the intense electric field close to the wire. In the less intense and uniform field typical of natural clouds, fragmentation of ice crystals is much less dramatic and cannot account for the phenomenon of ice crystal multiplication which takes place in cumulus clouds. On the other hand, electro-fragmentation could well contribute to the formation of ice crystals in thunderclouds. Consideration is given to the energy requirements of several mechanisms which might be responsible for the enhanced growth rate of ice in the direction of the electric field. Only charged water vapor molecules moving in the electrochemical potential gradient appear to have the necessary energy.