用AE-D卫星近地点上观测的n(He)估算湍流层顶高度

AN EVALUATION OF THE TURBOPAUSE ALTITUDE USING n(He) OBSERVED AT PERIGEES OF AE-D SATELLITE

本文分析了AE D极轨卫星近地点的变化及其相应的大气膨胀和密度分布情况 .在高度相同情况下 ,中低纬区热层底部的大气密度比高纬区大 ,卫星受阻也就更大 ,从而卫星近地点的高度在中低纬区比高纬区要低、白天比夜间低 .采用近地点上的n(He)观测资料 ,根据大气数密度在低层内均匀混合和高层内扩散分离的不同垂直分布特征 ,粗略地估算出湍流层顶的高度Zt 及其变化 .高纬区内Zt 高低与纬度几乎无关 ,但对磁暴的响应十分明显 .中低纬区内 ,Zt 随纬度减小而增大 ;白天地区Zt 大于夜间 ,而与磁暴的关系不大 .

In this paper, variations of AE-D's perigee altitudes, the corresponding atmospheric expansion and the density distributions are analyzed. At same heights but on different latitude areas, the density of the lower thermosphere is more intense at low latitude than that at high latitude. So does the satellite drag. Therefore, the perigee is lower at low latitude and it is lower by day than at night. Besides, the data of n(He) observed at perigees are used to roughly estimate the altitudes of the turbopause Z t and their variations according the two distinct vertical distributions of atmospheric composition in low and upper atmospheres: the homogeneous mixing and the diffusive separation. The results show that Z t is almost not related to latitude at high latitude areas, while its response to the magnetic storm is very clear. On the other hand, at low latitude areas Z t increases as the latitude decreases, and the value of Z t is larger by day than at night.