Fig. 4From: Simultaneous observations of equatorial plasma bubbles with an all-sky airglow imager and a HF Doppler sounding system in TaiwanAirglow data during Event 3 plotted in a format of keogram, which was created by extracting the all-sky images at the geographic latitude of RP1. Although obscured by clouds between 15:00 and 17:00 UT, four traces of eastward moving EPBs are identified as black linear structures extending upward to the right from 17:00 to 18:30 UTBack to article page