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Properties of the unusually short pulse sequences occurring prior to the first strokes of negative cloud‐to‐ground lightning flashes
Author(s) -
Kolmašová Ivana,
Santolík Ondřej,
Farges Thomas,
Rison William,
Lán Radek,
Uhlíř Luděk
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl060913
Subject(s) - lightning (connector) , thunderstorm , amplitude , pulse (music) , physics , meteorology , geology , atmospheric sciences , optics , power (physics) , quantum mechanics , detector
We analyze broadband magnetic and electric field measurements of pulse sequences occurring prior to first return strokes of negative cloud‐to‐ground lightning flashes. Our observations take place a few tens of kilometers from the thunderstorm but we also report the first simultaneous observations of preliminary breakdown pulses from a distance of 400 km. Their amplitudes reach up to 50% of the corresponding return stroke peak and typically decrease by ~40% during the sequences. A typical time interval between neighboring pulses was several tens of microseconds. We observe an unusually short duration of the prestroke activity (1–7 ms) reported for the first time during a summer thunderstorm, with a low height of initiation (3‐4 km). A very fast propagation speed (~10 6 m/s) is probably maintained for the entire prestroke process. A possible explanation can be based on a hypothesis of unusually strong negative charge sources in the observed thundercloud.