A comparison of intracloud and cloud-to-ground lightning discharges

Lightning discharges were investigated with high time-resolution equipment on both electric-field and electric-field-change meters. The analysis of the electrical records reveals that the late stages of intracloud discharges are very similar to those of cloud-to-ground discharges during the periods between successive return strokes (junction process) and during the period after the last return stroke (final process). In contrast, the initial portion of the field change of an intracloud discharge bears little or no resemblance to the initial portion of the leader field change of a discharge to ground. It is suggested that the difference in the initial breakdown characteristics results from variations in the relative populations of water drops and ice particles as they affect the internal impedence of the region of cloud where breakdown occurs. The difference in the initial field-change characteristics of intracloud and cloud-to-ground discharges is so distinct that from the first 10 msec of the electric-field-change record one can predict with over 95 per cent certainty whether a discharge will reach ground or remain within the cloud.