Short-duration upper atmospheric optical flashes were recorded on the night of 8 July, 1993 (9 July UT) from the NASA DC-8 Airborne Laboratory flying over the American Midwest. All-sky video images from an intensified silicon intensified target (ISIT) camera revealed 19 upper atmospheric flashes occurring over a period of ∼100 min. The flashes were similar in appearance to previously reported ground and shuttle-based video observations. Detailed analysis of 12 of the events yielded these parameters: (1) duration ≤17 ms; (2) brightness 10–50 kR, roughly that of bright aurorae; (3) terminal heights 30–100 km, with a mean of ∼60 km; (4) horizontal extent 10–50 km; (5) emission volume >1000 km³. The relative frequency of the optical flashes was (6) 1:200–1:400 compared to negative cloud-to-ground discharges and 1:20–1:40 compared to positive cloud-to-ground discharges.
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