Characteristics of the Lightning Stepped-Leader Electromagnetic Pulses

Abstract

Some characteristics and statistics of the electromagnetic fields produced by stepped-leaders just before cloud-to-ground lightning return strokes are described. A transient data acquisition system was used together with electric and magnetic field measuring devices with frequency bandwidths of 200 Hz to 1.6 MHz and 270 Hz to 2.3 MHz, respectively. In this recording mode, approximately 100 µs before the signal triggering, the transient data acquisition system could be recorded at a sampling time of 100 ns. The time intervals between peaks of the last leader pulse and return stroke field were widely distributed over the range of 5–70 µs, and the mean was approximately 16.2 µs with a standard deviation of 8.8 and 14.8 µs with a standard deviation of 5.2 for the positive and negative polarities, respectively. When the stepped-leader approaches closely to the ground, the time interval between leader steps tended to decrease with time. The mean peak amplitude ratio of the last leader pulse to the lightning return stroke field was 0.17±0.12 for the positive electric fields and 0.18±0.09 for the negative electric fields. On average, the full widths at half maximum of the stepped-leader pulses were 1.31±0.8 µs for the positive polarity and 1.71±1.12 µs for the negative polarity. All results presented here are somewhat different from those observed at other measuring sites, because lightning return stroke fields depend on geographical and meteorological conditions.

Unipolar and bipolar pulses emitted during the development of lightning flashes

“…They also speculated that the decreases of pulse amplitudes in the observed magnetic pulse trains are caused by decreasing current propagation speeds. Other studies investigating properties of pulse sequences have been published by, e.g., Gomes and Cooray [2004], Lee et al [2006], Nag et al [2009], or Baharudin et al [2012].…”

Properties of unipolar magnetic field pulse trains generated by lightning discharges

“…Trains of electric field and magnetic field pulses were found to be connected with various lightning phenomena. Preliminary breakdown pulses [ Nag and Rakov , ], stepped leader pulses [ Lee et al ., ], dart‐stepped leader pulses [ Davis , ], chaotic leader pulses [ Gomes et al ., ], pulses produced by bouncing‐wave‐type lightning discharges [ Nag and Rakov , ], and bursts associated with either K changes or M components were observed [ Rakov et al ., , ]. The shapes of individual types of pulses are generally similar, but the lengths of the rising and falling edges, the widths of the pulses, and the interpulse intervals vary from microsecond to millisecond scales.…”

Overview of Recent Progress in Lightning Research and Lightning Protection

“…Lee et al [43], [44], working in Korea, measured and characterized electric and magnetic field waveforms associated with return strokes and stepped leaders near ground. They presented data for both positive and negative lightning.…”