LIGHTNING ACOUSTIC SIGNATURE

The Faculte Polytechnique of Mons has participated in three programs o f artificially triggered lightning in Saint-Privat d'Allier (France, 1 986, 1990, and 1991). A close measurement (70 m) of the acoustic energ y emitted by a lightning stroke permits an assessment of different ele ctrical lightning parameters such as peak current, carried charge, and specific energy. Moreover, the spectral analysis of thunder confirms the cylindrical shock wave theory A. Few (1969, 1982) put forward a fe w years ago. The dominant frequency of the spectrum gives an estimate of the lightning channel energy per unit length.