ICC of Negative Upward Flashes to the Peissenberg Tower, Germany

Abstract:
Objective of the study is the Initial Continuous Current (ICC) of the negative upward lightning measured at the Peissen-berg Tower in Germany during the years 1992 to 2022. The lightning is categorized into four groups, i.e. the ICCRS-flash (at least one subsequent return stroke), the ICCP –flash (no subsequent return stroke, but at least one ICC-pulse of more than 2 kA), the ICCOnly –flash (no subsequent return stroke and no ICC-pulse higher than 2 kA), and the ICCBipolar –flash (negative ICC followed by at least one positive current component). The majority of 54.9% of them were ICCOnly–flashes, 24.0% of them were ICCRS-flashes, 19.6% of them were ICCP-flashes, and 1.5% of them were ICCBipolar –flashes. The ICCOnly-flashes (geometric mean GM = 25 C) were the weakest ones, the ICCP-flashes (GM = 102 C) were the strongest ones and the ICCRS-flashes (GM = 48 C) and ICCBipolar –flashes (63 - 69 C) were somewhere in between. About 8 % of the negative upward lightning had a charge higher than 200 C (LPL I of IEC 62305-1), with the maximum of 454 C. In 34.2 % of the cases, the ICC was superimposed by an initial current peak which exceeded the pure ICC by the factor of 4 on average. Approximately half of the ICCP-flashes (47.7 %), about one third of the ICCRS-flashes (33.3 %) and 28.9 % of the ICCOnly-flashes had such an initial current peak. Approximately 30 % of the self-initiated upward lightning and 42.3 % of the other-triggered ones exhibited the initial current peak. On average, the initial current peak had the maximum of 737 A, the peak duration of 33 ms, and the charge of 6.79 C. In 93.1 % of the cases, the initial current peak was superimposed by a pulse train which lasted up to 40.8 ms. The pulse train consisted of a series of high-frequent current pulses with amplitudes up to 4.5 kA.