A comparison between self-triggered and other-triggered upward lightning discharges

We have performed a detailed comparison between the self-triggered and the other-triggered upward lightning discharges in terms of their preceding electric fields, electric currents and charges transferred to the ground. We found that (1) the electric fields at which the upward lightning discharges occur are usually very low, like 2–4 kV/m at distances several hundred meters from the lightning occurring places, even for the self-triggered upward lightning; (2) the initial continuous current of self-triggered lightning tends to rise faster and to a bigger peak value than the other-triggered lightning, although both exhibit a wide range of rising time from 0.8 ms to 37 ms and a wide range of peak current from 0.1 kA to 15 kA; (3) both types of lightning transferred similar amount of charge to the ground with a range from several Coulombs to over 100 Coulombs.