Aggregation of Ice Crystals in Strong Electric Fields

Abstract

A RECENT series of experiments¹ has demonstrated that the adhesion of ice crystals on collision is a sensitive function of temperature, humidity and crystal-type. However, the effect of electric fields on the adhesion was not examined. Electric fields may have an important effect on the aggregation of ice crystals to form snow-flakes inside thunder-clouds where the crystal concentrations are high and fields of several thousand V/cm have been measured. It appeared possible that the attractive forces between the crystals, produced by polarization charging within the field and accentuated because of the small radius of curvature of the crystal edges, may produce increased aggregation which would be especially important under conditions close to the threshold, in the absence of a field, between adhesion and separation. The experiments described here were performed in order to test this hypothesis.