A study on the occurrence characteristics and sources of daytime ionospheric irregularities in the mid and low latitudes of the East-Asia region

In this study, we investigate seasonal and longitudinal variations in daytime ionospheric irregularities by analyzing total electron content (TEC) over the East Asian region during a period of low solar activity (2017-2021). To derive perturbation components of TEC, we subtracted the 1-hour running average from the TEC time series for each satellite-receiver pair. Seasonal variation of perturbation was quantified as the ratio of perturbation’s standard deviation to a 1-hour average of vertical TEC. Our findings indicate consistent peaks in GPS TEC daytime perturbation during winter across all studied years, aligning with Medium-Scale Traveling Ionospheric Disturbance (MSTID) activity in this region. To better understand the source and characteristics of daytime ionospheric irregularities in the East Asian sector and their relationship with MSTIDs and plasma bubbles, we compare our results with ICON satellite observations from 2020-2021. On the contrary, satellite observations of low-latitude daytime ionospheric disturbances during the low solar activity period (2020-2021) reveal peak electron density irregularities during the summer solstice in the East Asia sector. This discrepancy may stem from the height dependence of the source of the ionospheric disturbance source. It’s possible that at lower altitudes, MSTIDs have a more pronounced effect and are a primary source of irregularities, whereas at altitude over 600km, plasma bubbles can override the influence of MSTIDs on the ionospheric irregularity within that altitude range.