Solar and geomagnetic activity and seasonal dependence of global equatorial plasma bubbles based on GNSS observations

Equatorial plasma bubbles (EPBs) are large-scale ionospheric irregularities that typically occur at night over the magnetic equator and low latitudes. In this paper, the long-term GNSS observation data of the low-latitude regions from 2010 to 2021 are used to analyze the solar and geomagnetic activity and seasonal dependence of EPBs. The results show that the occurrence rate of EPBs in every longitude region is significantly positively correlated with solar activity, and the correlation coefficient between the daily occurrence rate of EPBs and the F-107 index is close to 0.70. In the range of longitude from -60 degrees to -30 degrees, the correlation between the occurrence rate of post sunset EPBs and F-107 has obvious saturation effect during high-occurrence months. The EPBs mainly occur in January-March and October-December of longitude from -60 degrees to -30, and typically occur in equinoxes over other longitudes. The seasonal asymmetry of the occurrence rate of post sunset EPBs in different longitude regions is significantly different. During the increasing phase of solar activity, the occurrence rate of EPBs in longitude -60 degrees similar to-30 degrees from October to December is much higher than that from January to March. During the decreasing phase of solar activity, the occurrence rate of EPBs in longitude 0 degrees similar to 180 degrees is higher in March equinox than that in September equinox. Additionally, geomagnetic disturbances mainly suppress the EPBs, especially in the high solar activity years and equinox seasons.