FACTORS AFFECTING THE ELECTRIC CHARGE ACQUIRED BY AN ICE SPHERE MOVING THROUGH NATURAL SNOWFALL¹

Abstract

The factors affecting the electric charge acquired by an ice sphere moving through natural snowfall have been investigated experimentally. When graupel particles were in the air the sphere always received a positive charge. If graupel was not present the sign of the charge appeared to be related to the direction of the atmospheric electric field.When the field was directed downwards the ice sphere received negative charge, and when the field was directed upwards the sphere received positive charge.The results are explained in terms of the direct transfer to the ice sphere of some of the net charge on the ice particles in the air making a glancing contact with the ice sphere. The charges that an ice sphere received by this mechanism appeared to be much larger than any charges that might have been generated by asymmetrical rubbing between the ice particles in the air and the surface of the ice sphere.

Role of relaxation and contact times in charge separation during collision of precipitation particles with ice targets

“…Superposed on the three previous mechanisms are the charge separation effects due to splintering, or secondary crystal production, and to inductive polarization by an external field. Depending on strength and sign of the latter, separation of inductively polarized charge by colliding particles may enhance or reduce charge separation by other processes [e.g., Buser, 1976]; it may become dominant [Shewchuk and Iribarne, 1974] and then determine the sign of overall charge separation [Hobbs and Burrows, 1966;Burrows et al, 1967;Scott and Hobbs, 1968;Pruppacher and Klett, 1978, pp. 601-605].…”