FAIR-WEATHER ELECTRICITY.

It is shown that the source current flowing out from a model thunderstorm cloud extends within an area 100 km horizontally in fair weather. Next the global circuit theory using the spherical harmonic function is reviewed to understand the global spreading of the thunderstorm-produced electrical potential. Then the quantitative estimation of global distribution of the electric field and the air-earth current is made by a simple equipotential ionsopheric model to see responses to changes of atmospheric conductivity and condensation nuclei. It is then shown where transition of the fair-weather electricity from the local type to the global type occurs. Refs.