Lightning Strokes in Field and Laboratory--II

Abstract
1. The lightning-stroke effects on paper, tracing cloth, porcelain, Micarta, and photograph negatives indicate an area (circular) for the core proportional to the current in the lightning discharge. This apparent area is, respectively, 0.08, 0.16, and 0.24 square inch for currents of 25,000, 50,000, and 75,000 amperes. Tests on fiber tubes at 140,000 amperes indicate an area of 0.44 square inch. 2. The surface fusion on copper plates, the photograph negatives, the glaze burning on porcelain, the record on Micarta, and other effects all show that the core is sustained the greater part of or the whole duration of the lightning-current discharge. The center part, some two-thirds or one-half, of the above-mentioned area comprises the core proper where the temperature is highest and maintained longer. Some expansion or variation in the core proper takes place during the discharge apparently resulting in the larger area. The actual current in the discharge (electrons for the greater part) naturally occupies but a fractional part of the core. The above records and observation suggest that the core structure is a complex of parts and processes. 3. When or as the current ceases the core then expands abruptly or explodes into the column. The expansion appears from the records relatively uniform (circular), the gases suffering a corresponding temperature drop with expansion. The later stages of the expansion process become turbulent in character. Thus for a current discharge of 50,000 amperes, uniform expansion apparently extends some one to 2 inches in diameter.

This publication has 12 references indexed in Scilit: