High-Speed Video Observation, Currents, and EM-Fields From Four Negative Upward Lightning to the Peissenberg Tower, Germany

In this article, we analyzed the optical images from high-speed video recordings and the time-correlated waveforms of the current, the electric field, and the magnetic field from four negative upward lightning which struck the Peissenberg Tower, Germany. Two of them were self-initiated ones and two of them were other-triggered ones. From the illumination in the video images, leader activity could clearly be detected during the occurrence of the first of the other-triggered lightning. In contrast, no illumination by leader activity could be found during the occurrence of the second other-triggered lightning and the time period of 2.5 s before. In addition, the current pulses superimposing the initial continuous current/continuing current were examined differing between those which developed in luminous or nonluminous branches. From the total of 26 current pulses which developed in nonluminous branches, 25 (96%) of them had a 10-90%-rise time less than 4 μs, and 23 (88%) of them had a 10-90%-rise time even less than 2 μs. Because the current waveforms resemble those of weak return stroke, we assume that the current pulses indeed represent the leader/return stroke mode of charge transfer to ground. The return strokes were extremely weak, with an arithmetic mean of 2.59 kA (GM: 2.08 kA) for the current peak. On the other hand, from the total of 74 current pulses which developed in already luminous branches, none of them had a 10-90%-rise time less than 4.4 μs. The arithmetic mean is 29.8 μs and the geometric mean is 20.5 μs. Due to the relatively long rise time, we assume that these current pulses represent the M-component mode of charge transfer to ground.