NO冷却率在连续磁暴中对热层密度的影响

Influence of nitric oxide cooling rates on thermospheric density during a succession of geomagnetic storms

基于CHAMP卫星加速度计数据,对2002年4月和2004年11月两个连续磁暴事件期间400 km高度热层大气密度时空变化特征进行了分析,结果表明,地磁扰动相近的连续磁暴发生时,热层密度对第一个磁暴的响应幅度明显大于后续磁暴;磁暴间歇期有时会出现密度低值;磁暴恢复相,热层密度先于ap指数快速恢复至暴前水平,甚至更低;热层大气经验模式NRLMSISE00的预测结果中没有包含这些现象.利用TIMED卫星SABER辐射计数据进一步分析同时段100~155 km高度NO冷却率的变化特点,NO冷却率在暴时的增大滞后热层密度2~6 h;磁暴恢复相,NO冷却率保持在较高水平,弛豫时间远大于热层密度.暴时增强的NO冷却率及其缓慢的恢复是导致热层密度响应幅度变小的原因,间歇期是否出现热层密度异常低值也与NO冷却率的增幅有关.

With the accelerometer data from CHAMP satellite during continuous geomagnetic storms occurring in April 2002 and November 2004,the Spatiotemporal evolution of thermospheric density at 400 km height has been analyzed.Results show that;during continuous geomagnetic storms,thermospheric density responds little to subsequent storm and lower density is found on interval between serial storms.Thermospheric density decreases more rapidly than ap index during storms recovery phase and become lower than pre-storm period.However,these abnormal phenomenons do not appear in the results of NRLMSISEOO atmospheric empirical model.Furthermore,using data from SABER on TIMED satellite nitric oxide cooling rates variations at 100~155 km height has been studied.It is found that the change of the NO cooling rates lags behind the thermospheric density by 2~6 h.During post-storm period,NO cooling rates remain higher than pre-storm period and the relaxation time is much longer than thermospheric density.Analysis suggests that the elevated NO cooling rates and its slow recovery are plausible causes for these thermospheric density abnormal phenomenons above.