激发态氮分子N_2在电离层中的作用的模拟研究  

A SIMULATION STUDY ON THE ROLE OF VIBRATIONALLY EXCITED NITROGEN N*2 IN THE IONOSPHERE

作　　者：张满莲[1] 史建魁[1] 尚社平[1] 

机构地区：[1]中国科学院空间科学与应用研究中心空间天气重点实验室,北京100080

出　　处：《地球物理学报》2004年第4期571-577,共7页Chinese Journal of Geophysics

基　　金：国家自然科学基金重大项目 ( 4 0 3 90 15 0 );中国科学院创新工程资助项目

摘　　要：激发态氮分子N 2 在电离层F区中起着重要的作用 ,它使F区占主导地位的O+ 离子的损失率增大 ,从而使该区的电子浓度减少 .本文利用理论电离层数值模型 ,通过考虑与不考虑N 2 的作用 ,对包括 1990年 6月、1997年 5月、1998年 5月以及 2 0 0 0年 4月磁暴事件在内的时间区间的电离层响应情形进行模拟研究 ,并与实测结果进行对比 .结果表明 ,N 2 对电离层电子浓度的影响在太阳活动高年非常明显 ,在太阳活动低年虽有些影响 ,但效果并不明显 ,其程度远不如高年 .在太阳活动高年 ,不仅是磁暴期间 ,在较宁静期间也必须考虑N 2 的影响 .而且 ,在考虑N 2 的作用时 ,还与激发态振动温度Tν 有关 ,在采用Tν=Tn(其中Tn 为背景中性大气的温度 )的简化处理时 ,所得结果与观测结果的符合程度不如对Tν 进行精确计算时所得的结果好 .模拟结果还表明 ,太阳活动高年 ,N 2 作用的结果主要是使 15 0km高度以上的F区电离层电子浓度减少 ,而对 15 0km以下高度的电离层电子浓度则影响不大 .另外 ,N 2 基本不影响F2 层峰高hmF2Vibrationally excited molecular nitrogen N * 2 plays an important role in the F region ionosphere by increasing the loss rate of the dominant ion O +, thereby reducing the electron concentration in the F region of the ionosphere. In this paper, we use a theoretical numerical ionospheric model to study the effect of N * 2 on the ionosphere during four time periods, each including both geomagnetically quiet and storm disturbed pe- riods, through considering and not considering the role of N * 2 in the numerical ionospheric model. The four periods simulated are (1) June 11～15, 1990; (2) May 14～20, 1997; (3) May 1～10, 1998 and (4) April 6～10, 2000. By comparing the simulated results with the observational ones, it is shown that N * 2 has a significant effect on the ionosphere during high solar activity years, while for the low solar activity years, the role played by N * 2 is very limited, much less than that in high solar activity years. It is also shown that for the high solar activity years, when constructing an ionospheric physical model, one must take into account N * 2 not only for the geomagnetically disturbed period but also for the quiet period. Moreover, it is found that the effect of N * 2 on the ionospheric electron density distribution depends on the vibrational temperature T ν adopted. When taking the value of T n as T ν (where T n is the background neutral temperature) the simulated result, compared with the observation one, is not as good as that when T ν is calculated by the steady state analytical solution. Moreover, our simulation results show that, for high solar activity years, the effect of N * 2 on the distribution of ionospheric electron concentration is to reduce the electron density for the height above 150km, while its effect on the electron density below 150km is very small. The F 2 layer peak height h mF 2 is not affected basically by N * 2.

关 键 词：电离层 数值模拟扰动机制 激发态氮分子的作用 

分 类 号：P352[天文地球—空间物理学]