Upward positive lightning measured at the Peissenberg Tower, Germany

Subject matter of the paper is the analysis of six upward positive lightning initiated from the Peissenberg Tower, Germany. All of them occurred during the cold season from February to April in the years 1997 to 1999. Three of them were initiated without nearby preceding lightning activity (called “self-initiated” upward lightning) and the other three occurred during nearby lightning activity (called “other-triggered” upward lightning). We assume that the other-triggered upward positive lightning was initiated by a preceding leader process in the thunder cloud. The other-triggered positive upward lightning was a kind of downward lightning involving a relatively long upward connecting leader. Such an extent of charge was accumulated in the downward leader branches that the electric field was high enough to initiate the upward connecting leader. The first current component, however, was different from the current of a first return stroke of a positive cloud-to-ground flash. The duration was 15.7 ms on average, with the maximum of 4.37 kA. Due to the long duration and the relatively low current, the first current component is more consistent with the initial continuous current of an upward lightning. The initial continuous current of the self-initiated upward lightning was superimposed by strong initial current pulses with peak values in the range of several kilo-amperes. The initial continuous current of the other-triggered ones was also superimposed by initial current pulses, but they were much weaker with peak values in the range of several hundreds of amperes. Stronger pulsation was observed only after the delay of about one millisecond.