Effect of electrical forces on charge separation caused by the combined effect of the precipitative and convective mechanisms in thunderclouds

Abstract

The maximum electric field that can be generated by the combined effect of precipitative and convective mechanisms in thunderclouds has been calculated. The derivation includes leakage currents produced by the electrical forces acting on precipitation and cloud particles. It is found that although these leakage currents significantly influence the charge separation process, very high electric fields, generally exceeding breakdown values, can be generated under moderately convective conditions. Dependence of the maximum electric field on updraught velocity, precipitation intensity, liquid water content, particle charges, etc., has been evaluated. The results demonstrate that while in nonconvective or weakly convective clouds, higher values of precipitation intensity can generate higher electric fields, in convective clouds with updraughts of about 0.5 m/s or higher, higher precipitation intensities saturate the electric field at lower values. Further, larger electrical charges on the precipitation and cloud particles generally lower the maximum electric field that can be generated. Limitations and significance of the results have been discussed in view of the simplified assumptions and available observations.