Engineering topics
Publications and source records attributed to Laroche, P..
An experiment was carried out in which 3-D mapping of VHF sources was compared to a 3-D description of the reflectivity and dynamics of associated cloud cells observed by a radar network. Data from 61 microbursts were analyzed and it was found that, in 93 pct. of the cases, electrical activity precedes outflow development. The results confirm that the peak in intracloud activity precedes the maximum value of the outflow.
Observations of a modified form of rocket triggered lightning are described. A flash triggered during the summer of 1989 is studied as part of an effort to model bidirectional discharge. It is suggested that the altitude triggering technique provides a realistic means of studying the attachment process.
Electrical measurements were conducted in 1987 and 1988 on streamer and leader discharges occurring during the first stages of a triggered flash. This paper describes the pulsing phenomenon observed at positive leader onset (typical pulsing rate 25 microns), and it is shown that the same process happened in the case of the ignition of a flash triggered in altitude; with a wire several hundred meters long, positive leader propagates alone for several ms before the ignition of the downward negative stepped leader.
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Presented in this paper are the main results of the 1987 Rocket Triggered Lightning Program (RTLP) in Florida: I greater than 60 kA, DI/DT greater than 400 kA/micro-S. Optical and electrical observations from flashes triggered by grounded wire or insulating cable (200 m) rocket technique are presented. Correlation between I and DI/DT measurements are presented and discussed. These measurements were carried out with the same grounded wire rocket technique in Florida in 1985, 1987, and in France in 1986.