Some Inferences From Radial Electric Fields Measured Inside the Lightning-Channel Corona Sheath

Radial electric field waveforms at a horizontal distance of 10 cm from the triggered lightning channel attachment point (inside the corona sheath) have been measured with a Pockels sensor. The electric field change during the leader stage was often overcompensated by the opposite-polarity electric field change during the return-stroke stage. The opposite polarity overshoot in radial electric field waveforms is consistent with the expected existence (during the return-stroke stage) of two concentric zones within the corona sheath: an inner zone containing net positive charge and an outer one with negative charge. The measured radial electric field waveforms exhibited quasi-exponential decay (very similar for all the waveforms), which was used for estimating the apparent electrical conductivity inside the corona sheath.