The free electrical charge on precipitation inside an active thunderstorm

The free electrical charges carried on individual precipitation particles were measured in an electrically active thunder-cloud at various altitudes up to 20,000 feet, using an aircraft and an improved induction method of measurement that avoided touching the particles. Data are given for the free electrical charge measured on the droplets and for the droplet space-charge density at seven different levels. Positive and negative charges were usually encountered at all levels, but sometimes only a single sign was observed in a specific area. With the freezing level at 14,000 feet, the maximum electrification occurred near 7,500 feet and at a temperature of +10°C. Here both the positive and negative charge approximated 0.27 esu per drop. The charge per drop at 5,000 and at 20,000 feet was less than one-fourth of this value. The electric field at the surface of the observed highly-charged droplets is a large fraction of the dielectric strength of air, showing that powerful electrifying agencies exist. The distribution of free charge inside an active thunder-cloud is relatively complicated.