CHAMP卫星观测的热层大气密度变化特征

Features of the thermosphere density at 400 km derived from the CHAMP

采用2001—2010年CHAMP(CHAllenging Minisatellite Payload)卫星高精度加速度计反演的热层大气总质量密度观测数据,对400 km高度大气密度的变化特征进行了分析与研究。结果表明,太阳辐射高低整体上控制着热层大气密度数值大小变化,在太阳宁静期热层大气密度受地磁活动控制,其最大值区域在地磁12—18时(地方时)内移动,重复周期为4~5个月,与地磁活动的Ap指数变化相似。对比经验模式与CHAMP卫星观测值,两者偏差纬向分布较均匀,经向变化明显;当太阳活动处于中低水平即F 10.7小于120时,模式值偏高5%~10%;当F 10.7大于130时,模式值偏低10%以上。为经验模式的改进提供相应的参考。

Total mass densities at 400 km altitude derived from the CHAMP(Challenging Minisatellite Payload)satellite are used to characterize the distribution and monthly variance of thermosphere density.Thermospheric density is affected by the solar activity.During the solar minimum,the density is mainly determined by the geomagnetic activity,and the maximum moves from 12 to 18 periodically.The period is about 4 to 5 months,similar with that of the Ap index.Comparison between the CHAMP dataset and the NRLMSISE00 empirical model shows that:the density ratio bias varies with latitude.An underestimation occurs in the south of S,while an overestimation in the north.When the solar activity is quite,the model is greater than the CHAMP measurements by 5%to 10%.If F 10.7 is larger than 130,the model is smaller by 10%.Under the quiet and moderate geomagnetic activities conditions,an overestimation of 10%occurs for most of the MLT.The bias also exhibits monthly variation,which is positive in winter and spring and is negative in summer and autumn.The secular statistics provide a valuable reference to improve the empirical model.