SOME FEATURES OF LIGHTNING FLASHES OBSERVED IN SWEDEN

Characteristics of lightning flashes in Sweden were measured by record ing the electric fields generated by the whole flash in microsecond re solution. The results were gathered from five thunderstorms occurring within 50-100 km from the measuring site. For negative ground flashes the geometric and arithmetic mean of the interstroke intervals were 48 ms and 65 ms, respectively. The corresponding values for the positive ground flashes were 64 ms and 92 ms, respectively. It was found that about 24% of the negative multiple-stroke ground flashes had at least one subsequent stroke with a peak electric field larger than that of t he first return stroke. Furthermore, about 15% of the subsequent strok es had peak electric field amplitudes larger than those of the first r eturn strokes. The geometric mean of the ratio of the subsequent strok e peak field to the first return stroke peak field was 0.5. The mean n umber of strokes per flash was 3.4 and 18% of the flashes were single- stroke flashes.