Brian D. Wright

A ground level gamma-ray burst observed in association with rocket-triggered lightning

energetic radiation was observed at much earlier times, up to 160 ms before the return strokes. Because for such times, the dart leader tip must have been about 1000 m above the ground, it cannot be ruled out that for these events a gamma-ray (>1 MeV) component also originated from the cloud. [3] In this paper, we report an unusual event that occurred during the last rocket-triggered flash of the 2003 season. For this flash, an intense burst of MeV gamma-rays was observed from a distance of 650 m from the lightning channel, not in association with the dart leader or return stroke, but in association with a large current pulse (11 kA) occurring during the initial-stage (during the initial continuous current), about 20 ms after the vaporization of the triggering wire. In triggered lightning, the initial-stage is characterized by a steady current, preceding the return strokes, with superimposed pulses up to several kA in amplitude [Wang et al., 1999]. Considering the large distance of the detectors and the high energy of the gamma-rays, it is plausible that the burst originated in the cloud processes, perhaps many thousands of meters above the ground. This result may greatly facilitate the study of runaway breakdown of air inside thunderclouds [Gurevich et al., 1992], since it implies that observations of this phenomenon from the ground at sea level may be practical.