Characteristics of channel base currents and close magnetic fields in triggered flashes in SHATLE

Statistical distributions of channel base currents and close magnetic fields have been investigated by using data measured during Shandong Artificially Triggering Lightning Experiment (SHATLE) from 2005 to 2009. Effects of different factors on close magnetic fields have been examined by using numerical method. Statistical results showed that return stroke peak currents varied from 5.8 kA to 45.7 kA with a geometric mean (GM) of 14.1 kA. The GM of 10–90% risetime, 30–90% risetime, and half‐peak width in current waveforms were consistent with most of the results found in the literature. The magnetic fields at 60 m, based on 32 return strokes, varied from 18 μT to 148 μT with a GM of 52 μT. The peak value of the 10–90% risetime in magnetic field waveform was between 1 and 2 μs with a minimum of 0.4 μs and a maximum of 8.4 μs, covering a relatively wide range compared with other studies. The numerical modeling results showed that for larger return stroke speeds, the magnetic field peaks are larger, half‐peak widths and risetimes are smaller. Effects of distance on time‐variation contribution of induction and radiation components are quite different from that of return stroke speed and current risetime. With increasing the distance or current risetime, the magnetic field peak decreases, but the risetime and half‐peak width increase.