No. 80: Mar-Apr 1992
A photodiode was recently lofted to high altitudes (over 400 kilometers) in an experiment to measure the optical power of lightning. During the 10-minute flight, more than 500 lightning-related events were recorded over that part of the globe visible from the rocket's altitude.
"Among these is a class of about 23 events all having an anomalous signature, with obvious clustering of optical impulses or continuous emissions, and resulting durations of several hundred milliseconds. Such durations are much longer than typical for lightning-related events recorded at the rocket, which are more frequent overall. Every anomalous optical event (AOE) was accompanied by broadband VLF signals of a distinctive character...In considering possible sources above 30 km we find that the AOEs do not seem to resemble other natural optical phenomena, such as meteors which burn up well above 30 km in the mid-latitude atmosphere."
(Li, Ya Qi, et al; "Anomalous Optical Events Detected by Rocket-Borne Sensor in the WIPP Campaign," Journal of Geo physical Research, 96:1315, 1991. Cr. C. Rush.)
Comment. Apparently these anomalous "flashes" have not yet been detected from the ground. The implication is that there are many more high-altitude electrical discharges than scientists expect or can account for.