利用TIE-GCM模式计算电离层电流及夜间电离层磁场

电离层电流产生的磁场是地磁场卫星测绘时需要剔除的干扰源.利用电离层热层模式TIE-GCM计算电离层中的中性风、重力驱动和压强梯度等形成的电离层电流的全球分布，分析电流在特定位置产生的磁场及磁场三分量随纬度的变化规律.结果表明，E层尤其是磁赤道和极区的电流密度较大，可达103nA·m-2量级，F层电流密度量级约为10nA·m-2.在磁静日（Kp≤ 1）夜间22:00LT-04:00LT，电离层电流在中低纬度（南北纬50°之间）产生的磁场量级为几个nT，且磁场的南北向分量和径向分量基本大于东西向分量.通过与CHAMP卫星磁测数据分析比较，发现TIE-GCM模式计算电离层干扰磁场在中低纬度可以取得较好的结果，但在高纬度地区的效果不理想，还需进一步改进模式以提高计算精度. 

Ionospheric currents and nightside ionospheric magnetic fields calculated by TIE-GCM

In geomagnetic field mapping, the magnetic fields generated by the ionospheric currents are sources of interference that should be removed. In this paper, the ionospheric currents generated by neutral wind, gravity drift and pressure gradient are calculated by Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The global current distribution is used to examine the magnetic field generated by the ionospheric currents at a specific location. The variation of the three components of the magnetic field with latitude has been analyzed. The results show that the current densities in the E layer, especially in the magnetic equator and polar regions, are as high as about 103nA·m-2, while the current densities in the F layer are about 10nA·m-2. The magnetic field between 50°N and 50°S induced by ionospheric currents is about several nT from 22:00LT to 04:00LT in the magnetic quiet day (Kp ≤ 1), and the north-south and radial components of the ionospheric magnetic field are substantially larger than the east-west component. By comparing with CHAMP observation data, it is proven that the TIE-GCM has good performance in calculating ionospheric currents and magnetic fields at low and middle latitudes. However, the results are not very good at high latitudes and TIE-GCM should be improved in order to increase the calculating accuracy.