Open AccessInitial leader velocities during intracloud lightning: Possible evidence for a runaway breakdown effect
Author(s) -
Behnke Sonja A.,
Thomas Ronald J.,
Krehbiel Paul R.,
Rison William
Publication year - 2005
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jd005312
Subject(s) - lightning (connector) , ionization , excited state , physics , flash (photography) , storm , meteorology , surge , mechanics , geology , computational physics , environmental science , atomic physics , optics , ion , power (physics) , quantum mechanics
Using three‐dimensional lightning mapping observations, the initial leaders of intracloud flashes have been found to start at a median speed of about 1.6 × 10 5 m s −1 and to decelerate during the first 10–15 ms of the discharge. The results disagree with the predictions that the speed should increase with time as the developing leader shorts out an increasing potential difference in the storm. The observations can be explained if the flash initiation region is preconditioned in some manner to give a high initial speed and if the preconditioning decays with time and/or decreases with distance to give the observed speed decrease. Such preconditioning could be the result of ionization and excited molecules produced by energetic electron avalanches.