A SEMI-ANNUAL VARIATION OF THE ATOMIC OXYGEN IN THE UPPER ATMOSPHERE

The long-term variation of the atmospheric composition in the Earth's upper atmosphere are controlled by 11-year cycle of the number of sunspots, varied solar and geomagnetic activity and so on. Satellite composition measurements showed that composition variations occurred. In this paper, the discussions are based on data from Satellite LDEF, and only represented in send-annual variation of the atomic oxygen (LDEF, spent 5 years and 10 months in LEO, from 1984 to 1990). The results show that a send-annual variation of the atomic oxygen is very clear, especially during the solar minimum (the mean annual sunspot number< 20). The density of the atomic oxygen changes 40%-60%, and the total amount of variations is further enhanced by the increasing of the sunspots number, while the change is up to 87% during the solar maximum (in 1989, the mean annual sunspots number > 120).