This distribution is profoundly influenced by the observed differences between the positive and negative light ion conductivities in the atmosphere. Electrification by induction frequently supplements these processes. Rain formed by the association of these cloud elements may be highly electrified and a mixture of positive and negative drops is usually produced. Experimentally well-established processes are considered that can selectively charge such rain or selectively discharge it. It is shown that either process can establish a free space charge distribution that is transferred toward the ground by gravity, and may be large enough to develop electric fields exceeding the dielectric strength of air.
Lightning then intervenes.
The conditions necessary to establish gross free charge distributions by regeneration are specified and shown to be met under frequently occurring meteorological situations. Many of the observed characteristics of thunderstorms are traceable to the nonuniform semiconducting nature of the lower atmosphere and its nonohmic behavior. The analysis reflects the results of earlier work.