On the radiation mechanism of magnetic pulses measured during the initial stage of rocket-triggered lightning

With the broadband low-frequency (LF) magnetic fields measured during the SHAndong Triggering Lightning Experiment (SHATLE) in 2013-2015, we examined the radiation mechanism for the magnetic pulses measured during the initial stage of rocket-triggered lightning. The micro-second magnetic pulses within 1 ms after the inception of positive leader are radiated by the downward propagation of current pulse along the triggering wire (usually longer than 100 meters); these magnetic pulses can be simulated with the transmission line model. For the burst of magnetic pulses measured during the initial continuous current, the radiation mechanism could be best interpreted by means of a dipole model. That is, these magnetic pulses are radiated by the small discharging events occurring typically over several meters around the tip of the ascending positive leader.