Analysis of Pulsating Aurora Periodicity Using e-POP/FAI Near-Infrared Observations

Disturbances in the ionosphere and upper atmosphere caused by high-energy particle precipitation can produce significant social and economic impacts, including GNSS positioning errors and satellite losses. Auroras, generated by collisions between energetic particles and atmospheric constituents, are important indicators of the near-Earth space environment. Among various auroral types, the pulsating aurora characterized by quasi-periodic brightness variations in patch-like structures, provides critical insights into the coupling processes between the magnetosphere and ionosphere. Despite their significance, comprehensive analysis has been hindered by the limited spatial coverage of ground-based observations and the sampling constraints of scanning-type satellite observations, making it difficult to continuously monitor the intrinsic periodicity of pulsating aurora on a global scale. In this study, we use near-infrared (NIR) observations from the Fast Auroral Imager (FAI) onboard the Enhanced Polar Outflow Probe (e-POP) to investigate the periodicity of pulsating aurora. We analyze 380 sets of e-POP/FAI NIR images acquired in 2015, together with DMSP/SSUSI ultraviolet images for contextual auroral identification. Our results show that the high-cadence imaging capability of e-POP/FAI effectively captures the temporal dynamics of pulsating aurora. Spectral analysis reveals dominant modulation periods of 4-6 s. These findings highlight the importance of high-temporal-resolution optical observations from low-Earth orbit for resolving the rapid evolution of pulsating aurora and provide a useful framework for investigating near-Earth space environments that are difficult to observe using conventional techniques.