Abstract
We have measured the correlated sub-microsecond E-fields and high-speed images of nine upward positive leaders occurred in winter from high grounded —structures at Hokuriku areas of Japan. It is found that all the leaders are initiated without any in-cloud discharge activity as their triggers. The average leader speeds we measured are around 106 m/s. All the leaders appear to contain a few pulses soon after their initiations. Pulse rise time ranges from 3.1 μs to 71.4 μs with a GM (Geometric Mean) value of 27.2 μs. Pulse decay time varies from 3.7 μs to 148.8 μs with a GM value of 30.9 μs. Pulse time duration distributes from 12.6 μs to 208.3 μs with a GM value of 59.8 μs. Most of the pulses are the same type of ICC (Initial Continuous Current) pulses. In addition, several correlations such as the light intensity just prior to each pulse versus pulse peak intensity are presented for the pulses.
