Detection of in-cloud lightning with VLF/LF and VHF networks for studies of the initial discharge phase

Hans D. Betz (1) , T. C. Marshall (2) , M. Stolzenburg (2) , Kersten Schmidt (3) , Wolf P. Oettinger (3) , Éric Defer (4) , J. Konarski (5) , Pierre Laroche (6) , F. Dombai (7)

1 Physics Department, University of Munich
2 Department of Physics and Astronomy, University of Mississippi
3 Nowcast
4 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
5 Institute of Meteorology and Water Management
6 ONERA - The French Aerospace Lab [Châtillon]
7 OMSZ - Hungarian Meteorological Service

Lightning initiation and the associated in-cloud parts of lightning flashes have been studied by comparing thunderstorm data from two independent networks, LINET and SAFIR-type systems, operating in the VLF/LF and VHF regime, respectively. The two networks respond to radiation pulses with different length scales; an event detected by VLF/LF must be hundreds of meters long. In all 12 storms studied, up to half of the first in-cloud events detected with the VHF networks were found to be closely time-correlated with the first VLF/LF signal. Range-normalized VLF/LF signal amplitudes of the time-coincident events (TCEs) are comparable to amplitudes of weak cloud-to-ground strokes. Without measured preparatory VHF emission activity, initial breakdown in TCEs seems to start directly with a strong discharge step producing signatures in VLF/LF records. The TCE data are consistent with lightning initiation via a runaway breakdown mechanism that extended over hundreds of meters.

Domaines: Astrophysique [astro-ph]

Hans D. Betz, T. C. Marshall, M. Stolzenburg, Kersten Schmidt, Wolf P. Oettinger, et al.. Detection of in-cloud lightning with VLF/LF and VHF networks for studies of the initial discharge phase. Geophysical Research Letters, 2008, 35, pp.23802. ⟨10.1029/2008GL035820⟩. ⟨hal-03742706⟩