By utilizing magnetic field measurements collected by CHAMP during the years 2001–2009, average characteristics of nighttime ionospheric zonal currents at middle and low latitudes are investigated. We provide for the first time the detailed dependencies of these currents on location, local time, season, and the level of solar activity. The main results obtained are (1) the nighttime zonal ionospheric currents at F‐region altitude, derived from the vertical magnetic component, exhibit on average height‐integrated current densities up to 10 mA/m. The amplitude varies quasi‐linearly with F10.7 flux level. (2) During equinoxes symmetric current systems at F‐region altitude are found in the two hemispheres. After sunset, eastward currents dominate at low latitudes, fading away toward midnight. After midnight regions of eastward currents are observed at midlatitude. During solstice seasons, eastward currents are enhanced in the summer hemisphere; westward currents are stronger in local winter. (3) Longitudinal variations of F‐region currents show clear wave‐1 patterns. This is related to the effect of the stationary planetary wave‐1 and the diurnal nonmigrating tide, D0. This dominant tidal signal, enhancing eastward currents over the Pacific region, appears at middle and low latitudes and during all seasons. (4) At the magnetic equator, signs of the equatorial electrojet (EEJ) are evident after 02:30 MLT. Intensity of westward currents in the narrow band increases toward sunrise. Longitudinal variations of the EEJ show a similar wave‐1 pattern as F‐region currents. Here the westward current density is enhanced over Africa/India. The EEJ wave‐1 modulation is strongest around June solstice.

中文翻译：

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由CHAMP推算出的平均电离层中低纬度夜间夜间纬向电流

利用CHAMP在2001-2009年收集的磁场测量结果，研究了中低纬度地区夜间电离层纬向电流的平均特征。我们首次提供了这些电流对位置，当地时间，季节和太阳活动水平的详细依赖性。获得的主要结果是（1）从垂直磁分量得出的F区海拔高度的夜间纬向电离层电流，平均高度积分电流密度高达10 mA / m。幅度随F10.7通量水平准线性变化。（2）在春分期间，在两个半球中发现了F区高度的对称电流系统。日落之后，东流在低纬度地区占主导地位，直到午夜逐渐消失。午夜后，在中纬度观察到了东流的区域。在冬至季节，夏季半球向东流增强；在当地冬季，向西流变强。（3）F区电流的纵向变化显示出清晰的波1模式。这与固定行星波-1和日非移动潮汐D0的影响有关。这种主要的潮汐信号增强了太平洋地区的东风，出现在中低纬度以及所有季节。（4）在美国中部时间02:30之后，赤道电喷（EEJ）的迹象很明显。窄带中的西流强度朝日出时增加。EEJ的纵向变化显示与F区电流类似的wave-1模式。在此，非洲/印度的西向电流密度增加。