A statistical analysis of equatorial plasma bubble structures based on an all-sky airglow imager network in China

This paper investigates the statistical features of equatorial plasma bubbles (EPBs) using airglow images from 2012 to 2014 from a ground-based network of four imagers in the equatorial region of China. It is found that (1) EPBs mainly occur during 21: 00-00: 00 local time (LT) in equinoxes. There is an asymmetry in occurrence rates between March (June) and September equinoxes (December solstices). (2) Most EPBs occur in groups of two to six depletions. The distance between adjacent EPB depletions is similar to 100-700 km, and the average is 200-300 km. The zonal extension of an EPB group is usually less than 1500 km but can reach 3000 km. (3) EPBs usually have a maximum drift velocity near 100 m/s at 21: 00-22: 00 LT in 9.5 degrees +/- 1.5 degrees geomagnetic latitude and then decrease to 50-70 m/s toward sunrise. (4) The averaged westward tilt angle of most EPBs (with respect to the geographic north-south) increased from 5 degrees-10 degrees to 23 degrees-30 degrees with LT between 20: 00 and 03: 00 LT, then decreasing to 10 degrees-20 degrees toward sunrise. (5) When 90< F-10.7 140. The maximum PMLE increases by 3.4 degrees-5.5 degrees when F10.7 changes from 90 to 190. (6) The EPB occurrence patterns and zonal drift velocities are significantly different from those at Kolhapur, India, which locates west to our stations by 20.0 degrees-32.0 degrees in longitude.