Aircraft and Rocket Triggered Natural Lightning Discharges

Electrostatic field measurements in thunderstorms were obtained from the “Roughrider” F-100F aircraft, and from above storms with a U-2 aircraft. Analysis of data associated with lightning strikes to or near the aircraft indicates that most of the strikes occurred in a transition zone from positive over negative charge to the reverse as indicated by the vertical electric field component and that they occurred in or on the edge of an intense negative space charge concentration at flight level. These transition zones and charge centers are closely linked to the precipitation and draft structure in the cloud. Data taken at cloud base and on the surface has also been used to indicate conditions for rocket-triggered lightning. Small wire-pulling rockets fired by LTRI were successful in triggering strokes at an altitude of several hundred feet when the over-water storm field was about 200 v/cm. The Apollo 12 vehicle triggered strokes at 6400 ft when the surface field was about 35 v/cm. Post-flight analysis of data obtained at Cape Kennedy and Patrick AFB indicates two or three natural intra-or inter-cloud lightning events had occurred within 30 km of the Cape in the 25 minute period prior to launch.