STATISTICS ON ARTIFICIALLY TRIGGERED LIGHTNING

The Faculte Polytechnique of Mons has participated in the last three p rograms of artificially triggered lightning in Saint-Privat d'Allier, France (1986 1990, and 1991). Measurements of the vertical part of the electric field E and electric field derivative (dE/dt) only 50 m from the discharge were made in 1990 and 1991. Our data, combined with tho se of the Centre National d'Etudes des Telecommunications, the Centre d'Etudes Nucleaires de Grenoble, and the Ecole Centrale de Lyon, lead us to a statistical study bf the electrical parameters obtained from a rtificially triggered discharges in Saint-Privat d'Allier. We define t he statistical distributions of these electrical parameter populations and establish some relations between them, We compare artificially tr iggered lightning with natural lightning and conclude that the trigger ed lightning strokes are very similar to the subsequent strokes of nat ural lightning. We also compare the Saint-Privat d'Allier triggered li ghtning with the Kennedy Space Center (Florida) triggered lightning. T he Kennedy Space Center is at sea level and has a high ground conducti vity. while Saint-Privat d'Allier is a mountainous country with strong resistivity. Main results are, for the current, 50 % of triggered str okes are higher than 12.1 kA in Florida (statistics of 305 strokes) an d 9.8 kA in Saint-Privat d'Allier (54 strokes); for dI/dt, 50 % Of tri ggered strokes have a dI/dt higher than 91.4 kA/mu s in Florida (134 s trokes) and 36.8 kA/mu s in Saint-Privat d'Allier (47 strokes); 5 % of the strokes have a dI/dt higher than 297.7 kA/mu s in Florida, The be st relation (best correlation coefficient) between (dI/dt (kA/mu s) an d I (kA) is dI/dt = 2.6 I-1.34 in Florida (134 strokes) and dI/dt = 2. 0 I-1.28 in Saint-Privat d'Allier (47 strokes).