The Characteristics of the Abnormal Day-to-Day TEC Variation above East Asian Region

Abstract

We investigate the abnormal day-to-day variability of total electron content (TEC) over 60 Global Navigation Satellite System (GNSS) stations above the East Asian region from 2012 to 2018 and find that the positive anomalies occur more frequently at the middle latitude at about LT 14–20 and occur frequently around 28° N at about LT 22–00. The negative anomalies occur more frequently at the middle latitude at LT 10–02, and they obviously occur less frequently at about 15° N~30° N and LT 08–12, and occur less frequently near about 22° N~30° N and LT 14–18. The quantities of positive anomalies and negative anomalies are comparable. The direction of moving anomalies is from east to west in a zonal direction in all conditions. The moving speeds of anomalies are around 15~19 degrees per hour in the zonal direction and seem to grow as the latitude increases. TEC anomalies occur in 22.1% of temporal bins before large earthquakes within seven days and occur in 24% of temporal bins in the interval, which is within one day before and three days later than the main phase of geomagnetic storms. Further work is necessary to determine the sources of these anomalies.