Self-initiated and other-triggered positive upward lightning measured at the Peissenberg Tower, Germany

Abstract

Subject matter of the paper is the analysis of the total of six positive upward lightning initiated from the Peissenberg Tower, Germany. Three of them were so-called "self-initiated" upward lightning without nearby preceding lightning activity. The other three were so-called "other-triggered" ones which occurred during nearby lightning activity. It appears that the other-triggered ones were downward lightning involving an extremely long upward connecting leader. The arithmetic means were 2.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> m/s for the leader velocity and 1.02 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> C/m for the leader charge density. The first current component, however, was more consistent with the initial continuous current (ICC) of an upward lightning. The arithmetic means for the current duration, the current maximum and charge were 15.7 ms, 4.37 kA, and 13.3 C. The ICC started with an initial slowly rising section lasting about one millisecond. During this initial period the ICC was rather low in the range of several tens up to more than one hundred of amperes and superimposed by a series of very weak current pulses. The arithmetic means of the pulse peak, the pulse duration, the pulse charge and the inter-pulse interval were 0.49 kA, 9.6 μs, 1.76 mC, and 22.7 μs. After the initial slowly rising section, the ICC suddenly increased to several kilo-amperes. During this subsequent section, much stronger current pulsation occurred. The arithmetic means were 5.3 kA for the pulse peak, 46.6 μs for the pulse duration, 93 mC for the pulse charge, and 49.4 μs for the inter-pulse interval. The ICC of the self-initiated upward lightning did not have such an initial slowly rising current section with weak superimposed current pulses. The ICC immediately increased to several kiloamperes involving strong current pulsation. For the ICC, the mean values were 58 ms for the duration, 6.4 kA for the maximum, and 105 C for the charge. For the superimposed current pulses, the mean values were 5.7 kA for the pulse peak, 19 μs for the pulse duration, 53 mC for the pulse charge, and 23 μs for the inter-pulse interval. For the upward leader, the charge densities were in the range of 10 mC/m or even more. This value is about one order of magnitude higher compared to the charge density of the other triggered positive upward lightning.