Current and close EM field of rocket-triggered lightning flashes in SHATLE 2005–2010

Shandong Artificially Triggering Lightning Experiment (SHATLE) has been conducted continuously since the summer of 2005. During the six years from 2005 to 2010, twenty-two negative lightning flashes containing eighty-eight return strokes were successfully triggered. Channel base currents, close electromagnetic fields and high-speed camera images were obtained simultaneously for some of the strokes. Based on directly measured currents for thirty-six return strokes, the geometric mean of return stroke peak current was about 12.1 kA with a maximum of 41.6 kA and a minimum of 4.4 kA, the half peak width of current varied from 1 to 68 μs, and the geometric mean values of 10%-90% risetime, charge transferred and action integral were about 1.9 μm, 0.86 C and 2.6 ×10³ A² s, respectively. The electric field at 30 m caused by a return stroke with peak current of 16.5 kA reached 56.0 kV/m. The geometric mean of magnetic field at 60 m was about 52 μT.