Magnetic field measuring system and current retrieval in artificially triggering lightning experiment

A magnetic field measuring system with two rectangular loops perpendicular toeach other is developed and used to detect the total horizontal magnetic field producedby lightning discharges. Two sets of antenna with low gain and high gain aredesigned separately in order to obtain both small and large signals. The systemwas tested experimentally in a high-voltage laboratory, and the results showthat the system is reliable, and the waveforms detected by the system are very similarto the source current. The corresponding maximum current that can be measuredby the system with low gain antenna and high gain antenna locating at a distanceof 60 m from a lightning channel, is about 84.4 kA and 37.7 kA, respectively.For artificially triggered lightning flashes the magnetic field waveforms detectedat 60 m from the channel reflect quite well the channel base currents. UsingAmpere’s law of magnetostatics, the inferred currents from the magnetic fieldsfor three artificially triggered lightning return strokes were 39.8 kA, 29.1 kA and43 kA, respectively, which are close to the directly measured results of 41.6 kA,29.6 kA and 38 kA at the base of the discharge channel. The system can be a usefultool in the research of close electromagnetic environment of lightning flashes.