Electric field close to lightning channel in the presence of current reflections from the ground

Appearance of an overcompensated positive electric field in most vertical field measurements performed very close to the channel core is explained using the extended generalized traveling current source (extended GTCS) return stroke model with current reflections from the ground. New effects in the corona sheath due to the reflection of current pulses have been noted and taken into account. The channel-base current is separated into two components. The first current component is fast and with a greater peak value, while the second component is slower and with a lower peak. We've analyzed a return stroke for which the channel-base current and the electric field waveform very close to the triggered lightning are measured simultaneously. A new charging function is calculated according to the extended GTCS model, as well as the value of the ground reflection coefficient for the analyzed stroke. On one hand, new results are obtained through calculations of the channel charging function. On the other, the calculated values of the ground reflection coefficient confirm the results reported in other independent studies performed in natural or laboratory conditions. Finally, the concept of the extended GTCS model, that takes into account current pulse reflections from the ground, is proved to be correct.