Observations of upper atmospheric optical flashes recorded from an aircraft

Abstract

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.