Concurrent observations of auroral activity and a large sporadic sodium layer event during ANLC‐93

Prominent sporadic sodium (Na s ) layers, apparently associated with intense auroral activity, were observed during the 1993 Arctic Noctilucent Cloud Campaign (ANLC‐93) with an airborne sodium lidar on the August 6 flight near 51°N latitude. The peak density of the Na s layer reached 74,500 cm −3 . The zonal extent of the Na s layers exceeded 1600 km. Strong auroral emissions were recorded with an all‐sky imager on the aircraft. A Michelson Interferometer was used to measure the intensity of OH nightglow between 85–90 km. OH rotational temperature exhibited no obvious correlation with the Na s layer peak density near 94 km. The data suggest a connection between the Na s layers and auroral electron precipitations. The data also support the conjecture that dust and smoke particles may play a crucial role in the Na s layer formation.