中文摘要：

本文统计分析了2001—2005年的39次大磁暴事件（Dst〈-100nT）期间TIEGCM模式和CHAMP卫星大气密度数据.研究结果表明,模式结果与实测数据具有较好的一致性,但仍存在一定的偏差.大气密度及增量与SYM-H指数相关性较好,并且随纬度、光照条件和地磁活动水平变化.模式低估了磁暴期间大气密度的增幅,特别是在地磁活动水平较强时模式与实测的偏差较大.模式的偏差在高纬地区高于低纬地区,日侧高于夜侧.Dst指数越低,偏差越大,而当Dst指数低于-150nT以后,绝对偏差和相对偏差变化不明显.

英文摘要：

The spatial distribution of the thermospheric density would change greatly due to the particle precipitation during geomagnetic storms.These changes in thermospheric density cause the increases of air drag on low altitudes satellites,which will impact on the orbit and attitude of the satellites.Therefore,studies on the characteristics of the storm-time thermospheric density perturbation and the accuracy of thermospheric models are of great importance for both research and application meaning.In this article,the thermospheric densities at 410 km are simulated by the Thermosphere Ionosphere Electrodynamics General Circulation Model（TIEGCM）during 39 major geomagnetic storms（Dst〈-100nT）from 2001—2005,and compared with the densities observed by the CHAMP satellite.The deviations between TIEGCM and CHAMP are studied with different latitudes,sunlight conditions and geomagnetic indices,in order to examine themodel accuracy of forecast.The statistical results show that,（1）the model results have a good agreement with the observational data during geomagnetic storms.However,some deviations do exist.（2）The storm-time thermospheric densities at 410 km have fine correlationship with the SYM-H index,and vary with latitudes,sunlight conditions,and geomagnetic indices.The differences of density changes between dayside and nightside are smaller than those of absolute values.The densities calculated by TIEGCM show the similar response to the SYM-H index,except for the smaller values.（3）The TIEGCM underestimates the magnitude of the density perturbation during geomagnetic storms,especially for those at high geomagnetic active levels.The deviations of modeled densities from the observed densities in the high latitude region are larger than those in the lower latitude region.They are also bigger on the dayside than those on the nightside.The deviations increase with the Dst index absolute value until the Dst reaches-150 nT.The deviations show little relativity with the SYM-H index.The statistical results have l