Neutral atmospheric composition measurements daring the Western European Winter Anomaly Campaign 1975/76

Abstract The neutral atmospheric composition and structure were determined over ‘El Arenosillo’ (37°6′N, 6°44′W) during the Western European Winter Anomaly Campaign 1975/76 by mass spectrometric measurements. Two different types of mass spectrometers were launched on 4 and 21 January 1976 around 1430 and 1530 UT, on both days measuring the number density profiles of N 2 , O 2 , O, Ar, and CO 2 in the altitude range from about 80 to 117 km. The 2 days are characterized by high radio wave absorption. The main result is an enhancement of atomic oxygen densities by factors of 3–5 on 4 January compared with 21 January in the altitude region of 80–110 km. The N 2 and O 2 density profiles on both days show structures with deviations from CIRA (1972) up to 50%.