The Slow-Varying Electric Field of Negative Upward Lightning Initiated by the Peissenberg Tower, Germany

This paper analyzes the slow-varying electric fields and the associated currents of a total of 35 negative upward lightning initiated by the Peissenberg tower, Germany. Thirty-four of which were from winter upward lightning and only one from summer upward lightning. It appears that all of the winter upward lightning were initiated without nearby preceding lightning activity (called “self-initiated” lightning) and only the summer lightning was triggered by nearby lightning activity (called “other-triggered” lightning). The slow-varying electric fields of the winter upward lightning showed a fast rise characterized by the 10-90% risetime, with an arithmetic mean of 13.8 ms. After attaining the maximum, the electric field turned into a slow decay being characterized by the time on half value which was evaluated to having the arithmetic mean of 441 ms. Transported charges to ground were on average 44.8 C and on maximum 165 C. The maximum value of the electric field was 39.9 kV/m on average, with the highest value being 64.5 kV/m. For the electric fields, higher values were prevented by recovery effects such as the corona from objects at ground and the redistribution of the charge in the thundercloud. Due to these effects, no or only weak correlations were found between the 10-90% risetime, the time on half value, the charge, and the maximum of the electric field. From additional measurements with a field mill, it was found that the electric field recovers to the starting level within some seconds.