Changes of thermospheric composition and the response of the ionosphere during the magnetic storm of January, 1974

Data taken by the Atmosphere Explorer C satellite (AE-C) during a geomagnetic storm are used to investigate the changes of thermospheric composition and ionospheric plasma density. The storm time variations of the density of molecular nitrogen, atomic oxygen and oxygen ions are observed in middle latitudes (580 and 470 N) and low latitudes (210 and 100 N). A comparison between observation data and the MSIS-86 neutral thermospheric model is made, and a direct correlation between the changes in the ratio of O/N2 and in the density of 0+ is found. Some mechanisms causing these changes are discussed. (author)