Two-Step Method for Determining the Solar Quiet Current Focus and the Validation Using Observing Procedure Experiment

It was known that the Solar quiet (Sq) current is important for the ionosphere dynamics, which can cause variations in the geomagnetic fields recorded on the ground. Using a north-south chain of observatories, the latitude of the Sq focus (center of the solar quiet current) can be determined in a local area. However, a single chain of observatories does not provide the longitudinal information of the Sq focus. In this study, we proposed an improved method using a magnetic observatory network in Asia to determine the focus automatically. After taking the variability and asymmetry of the Sq current into consideration, the proposed method determines the Sq focus with the longitudinal and latitudinal fitting processes. To verify the effectiveness of this method, we designed an observing procedure experiment (OPE) to simulate the geomagnetic field observation and focus determination under different conditions. The results show that the proposed method has the capability of tracking the trajectory of the Sq focus. Additionally, the OPE can efficiently validate the performance of the method.