在太阳静日期间，中低纬电离层中电流体系主要包括Sq电流、赤道电集流(EEJ)和半球间的场向电流（IHFACs）。Sq电流的研究工作已经持续了几十年，在理论和观测研究方面比较成熟。虽然EEJ电流在位置上与Sq电流紧密相邻，但其产生机制则完全与Sq不同，而且EEJ与Sq之间的相互关系至今存在较大争议。IHFACs产生于Sq南北半球两个电流涡间的电势差，其研究工作相对较少，缺乏足够的认识。本项目拟采用地面与卫星联合观测的方式，使用全球中低纬台站磁场观测数据计算Sq电流，使用Swarm高精度高分辨率磁场观测数据计算EEJ和IHFACs电流，给出Sq电流、EEJ以及IHFACs电流在季节和地方时的分布特征，并通过相关分析进一步研究三者的相互联系和作用。这对于深入了解太阳静日期间的磁场变化特征、增强对磁层—电离层耦合的认识具有重要意义。

During the solar quiet period, there are Sq current, equator electrojet and inter-hemispheric field-aligned currents in the middle and low latitude ionosphere. The study about the Sq current has lasted for several decades. And it is mature in theory and observation. Although the EEJ locates near the Sq current closely, it is quite different from Sq current in generation mechanism. The relationship between them is controversial until now. IHFACs come from the potential difference between the Sq current vortexes in the north and south hemisphere. The study for the IHFACs is relatively scarce. There are not enough realizations about the IHFACs. In this project, the combination data from the ground and satellite will be used. The geomagnetic field data from global middle and low latitude observatories is to calculate the Sq current. The EEJ and IHFACs are obtained from high accuracy and resolution magnetic field data in Swarm satellite. Thereafter, the seasonal and local time character of Sq current, EEJ and IHFACs is studied. The relationship to the three current systems is also investigated through correlation analysis method. It is much significant to understand the feature of the geomagnetic field and coupling between the magnetosphere and ionosphere in the solar quiet period.