The origin of the prenoon-postnoon asymmetry for Sq current system
Sq电流系午前午后不对称性现象的来源

The solar quiet variation(Sq)is one typical kind of the variable magnetic field of the Earth.The feature of Sq reflects the structure of electricity and high altitude atmosphere tide in ionosphere.The variation of Sq takes an important role of understanding the process in coupling of ionosphere-thermosphere.It is necessary to separate the Sq correctly from the geomagnetic field in order to estimate the geomagnetic indices(such as the Dst,Kp and AE indices)and forecast the level of geomagnetic activity.In this paper,the geomagnetic field data observed by ground-based observatories are used to analysis the configuration of Sq,the prenoon-postnoon asymmetry,and the daily variations of Sq depended on the latitude and solar zenith.The results indicate that the asymmetry of Sq is resulted from interaction between the current systems in low and high latitude regions.