第23太阳活动周热层大气密度对太阳辐射指数F10.7响应的模拟研究

利用NCAR-TIEGCM计算了第23太阳活动周期间（1996—2008年）400km高度上的大气密度，并统计分析大气密度对太阳辐射指数FF_10.7的响应.结果表明，在第23太阳活动周内，大气密度的变化趋势与太阳辐射指数FF_10.7的变化趋势基本一致，但是大气密度在不同年份、不同月份对太阳辐射指数FF_10.7的响应存在差异.第23太阳活动周内太阳辐射极大值和极小值之比大于4，而大气密度的极大值与极小值之比则大于10.太阳辐射低年的年内大气密度变化不到2倍，而太阳辐射高年的年内大气密度变化可达2倍甚至3倍.大气密度与FF_10.7指数在北半球高纬的相关系数比南半球高纬的相关系数大.在低纬地区，太阳辐射高年大气密度与FF_10.7指数的相关系数比低年的大.不同纬度上，大气密度与太阳辐射指数FF_10.7的27天变化值之间的相关系数都大于其与81天变化值之间的相关系数. 

TIEGCM Numerical Study on the Thermospheric Density Response to Solar F10.7 Radio Flux Variations during the 23rd Solar Cycle

Thermospheric densities at the altitude of 400km during the 23rd solar cycle (1996—2008) are calculated using the NCAR-TIEGCM. The modeled responses of thermospheric density to solar radiation index F_10.7 variations are statistically analyzed. The results show that during the 23rd solar cycle, the variations of thermospheric density are basically consistent with those of F_10.7. However, the responses of thermospheric density to changes in F_10.7 are different in different years and months. The increase of solar radiation from solar minimum to maximum is more than a factor of 4 in the 23rd solar cycle, and the increase of thermospheric density from solar minimum to maximum is more than a factor of 10 during the same interval. The intra-annual density variations in the solar minimum years are less than a factor of 2 between density minimum and maximum, whereas those in the high solar activity years can be greater than a factor of 2 or even 3. The correlation coefficients between the thermospheric mass density and the F_10.7 index in the middle and high latitudes of the Northern Hemisphere are larger than those in the middle and high latitudes of the Southern Hemisphere, exhibiting an evident norther-south asymmetry. In the low latitudes, the correlation coefficients between the thermospheric mass density and the F_10.7 index in high solar activity years are larger than those in solar minimum years. At different latitudes, the correlation coefficient between the thermospheric density and the 27-day variation of F_10.7 is greater than that between the 81-day variations of thermospheric density and F_10.7.