Abstract
The sources of the electrical charges acquired by ice spheres rotated through natural cloud or precipitation particles are considered. In general, the steady charge that a sphere receives in such experiments derives from collisions with particles in the air and from the electrical coupling of the sphere with the ground.
The results of a number of experimental measurements on the charging of ice spheres whirled through natural snowfalls are described and analyzed. The average charge acquired by the ice sphere per ice particle collision was always negative over the range of temperatures investigated (−2 to −8C) and reached a maximum negative value of about 1.5×10−4 esu at −7C.
It is pointed out that if natural hailstones falling through cumulonimbus clouds receive charges due to collisions with ice crystals which are similar in magnitude to those measured in these experiments, this mechanism would readily explain the electrification of thunderstorms.
