%0 Journal Article
%A Sterpka, C.
%A Dwyer, J.
%A Liu, N.
%A Hare, B. M.
%A Scholten, O.
%A Buitink, S.
%A Veen, S. ter
%A Nelles, A.
%T The Spontaneous Nature of Lightning Initiation Revealed
%J Geophysical research letters
%V 48
%N 23
%@ 0094-8276
%C Hoboken, NJ
%I Wiley
%M PUBDB-2022-00619
%P GL095511
%D 2021
%X Here, we present new radio interferometer beamforming observations of lightning initiation using data from the Low-Frequency Array (LOFAR). We show that the first lightning source in the flash increases exponentially in intensity by two orders of magnitude in 15 μs, while propagating 88 m away from the initiation location at a constant speed of 4.8 ± 0.1 × 10<sup>6</sup> m/s. A second source replaces the first source at the initiation location, and subsequent propagation of the lightning leader follows. We interpret the first source to be a rapidly propagating and intensifying positive streamer discharge that subsequently produces a hot leader channel near the initiation point. How lightning initiates is one of the greatest unsolved problems in the atmospheric sciences, and these results shed light on this longstanding mystery. 
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000730019700047
%R 10.1029/2021GL095511
%U https://bib-pubdb1.desy.de/record/474239