Solar radiation is the main source for heating the thermosphere. The change of radiation intensity can result in the change of Earth＇s upper atmospheric density. With the same reason, the cycle of solar activities is the main factor to cause the corresponding cycle of thermosphere density change. The consequent change of atmospheric density directly influences orbiter＇s running and the precision of prediction of orbits of satellites. On the other hand, change of atmospheric density result from cycle of solar activities has something to do with different factors of solar-terrestrial physics, 5ome related phenomena should be taken into account. Although data of atmospheric density detectors which were onboard SZ-2 and SZo3 have already been used to discuss the change of upper atmospheric density, due to limit of their period on running, there are only a few descriptions of medium-term change. In this paper, the data of thermosphere density collected by the Atmospheric Density Detector onboard the satellite with the orbit altitude in 550-600 km. The results show that the value of thermosphere density has two kinds of cycle change, the length of one kind of cycles is 27 days, and the other is close to half a year. The results also show that the difference of the atmospheric density between the sunshine and shade area is one of the principal change of thermosphere density, the ratio of atmospheric density in the sunshine to the density in the shade correlates with solar activity.
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