Charge Distribution in a Quasi-Static Thundercloud Model

An analysis is made of the charge distribution in a quasi-static thundercloud system with the assumptions that, (1) the cloud has a charge separation mechanism at its midpoint and (2) the conductivity within the cloud is reduced by a given fraction from the free-air conductivity remote from the storm. The charge separation mechanism produces the primary positive dipole of the storm. The analysis shows that the growth of the charge in the central cloud primary dipole is accompanied by the development of shielding layers of opposing sign charge at and about the cloud-air interface. A positive shielding charge distribution is established at the cloud base while a negative charge shielding distribution occurs about the upper cloud. The analysis permits an evaluation of the limiting charge magnitudes that exist outside the cloud boundary as a result of the unbalance of the positive and negative ion concentrations, and those that exist inside the cloud boundary principally as the result of deposition of charge on cloud particulars. The lower positive shielding charge completely accounts for the positive charge center often observed in the base of storms. The growth rates and total charge of the shielding charge distributions approximate the growth rate and total charge of the primary dipole. Following the lightning discharge, the shielding layer charge readjustment occurs at a more rapid rate, determined principally by the free-air conductivity.