Characteristics and correlation of return stroke, M component and continuing current for triggered lightning

• The channel base current of triggered lightning has been measured and analyzed.
• The characteristics of RS, M component and continuing current were given.
• M components and RS play a key role in the duration of continuing current.
• “Restricted zones” were found in the correlation of M component, RS and CC.

Based on the channel-base current acquired from Guangdong Comprehensive Observation Experiment on Lightning Discharge (GCOELD), the characteristics and correlation of return stroke (RS), M component and continuing current (CC) were analyzed. As for RS, the geometric average values of peak current (PI), half-peak-width (HPW), rise time (t10–90%) and charge transfer within 1 ms after the beginning of the RS (Q1ms) are 16.41 kA, 17.03 μs, 0.43 μs and 1.62 C, respectively. As for M component, the geometric average values of PI, duration, t10–90%, HPW and charge transfer from the beginning to the end (Q) are 185.75 A, 1.68 ms, 0.42 ms, 0.70 ms and 0.11 C, respectively. As for CC, the duration, average current and charge transfer are 19.01 ms, 202.58 A and 3.85 C. 66% RSs in triggered lightning are followed by CC processes. And the percentages of long CC (duration ≥40 ms), short CC (10 ms< duration < 40 ms) and “questionable” CC (duration ≤ 10 ms) are 34%, 27%, 39%, respectively. Also, the effects of RS and M component on CC duration have been investigated. An interesting phenomenon of “restricted zone” which indicates that M components with small mean amplitude (<0.5 kA) is a necessary factor for the existence of long CC, has been found. It is possible that there are two types of M components which can exert different effect on CC duration. In addtion, we also found three “restricted zone” phenomena which exist in the correlation between peak current, charge transfer, action integral of RS and CC duration. The phenomena indicate that the peak current, transferred charge in 1 ms and action integral of RS are inherently correlative to CC duration. Especially for action integral of RS, it plays a more key role in the duration of CC. If the value of action integral is larger than 6300 A2 s, the long CC is highly unlikely to occur.