Charge Separation Associated with Secondary Ice Crystal Production

J. Hallett Desert Research Institute, Reno, Nevada 89506

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C. P. R. Saunders Department of Pure and Applied Physics, University of Manchester Institute of Science & Technology, Manchester, England

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Abstract

Laboratory studies of rime growth on a moving rod under conditions of secondary ice crystal production show that the rod acquires a positive charge, equivalent to charge associated with each ejected particle of 5 × 10−4C. Ice crystals produced by seeding also impart a positive charge to the rime, equivalent to a charge per particle of 5 × 10−16C. As the water vapor supply is cut off, the charge sign reverses. The results suggest that the sign of the charge transfer depends on the physical state of the rime surface and its vapor pressure excess or deficit relative to the environment. Charge separation in convective clouds is critically dependent on the changing proportion of graupel and small secondary ice crystals.

Abstract

Laboratory studies of rime growth on a moving rod under conditions of secondary ice crystal production show that the rod acquires a positive charge, equivalent to charge associated with each ejected particle of 5 × 10−4C. Ice crystals produced by seeding also impart a positive charge to the rime, equivalent to a charge per particle of 5 × 10−16C. As the water vapor supply is cut off, the charge sign reverses. The results suggest that the sign of the charge transfer depends on the physical state of the rime surface and its vapor pressure excess or deficit relative to the environment. Charge separation in convective clouds is critically dependent on the changing proportion of graupel and small secondary ice crystals.

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