Ultralow frequency waves in the South Atlantic anomaly: Application of FY-3E observations

On 5 July 2021, the China FY-3E satellite was successfully launched, equipped with instruments to measure ultralow frequency waves (ULF) and charged particle populations deep within the magnetosphere. In this study, we report two ULF wave events observed by the FY-3E satellite, which are closely associated with magnetospheric substorms, in conjunction with observations from the Swarm satellite. We noticed a significant similarity between the ULF waves recorded by FY-3E and Swarm, indicating that these satellites captured the same wave events. The presence of a 180° phase shift across L shells and an oscillating field aligned Poynting flux suggest that the observed ULF waves exhibit characteristics of field line resonance (FLR). This work also characterizes essential differences in the behavior of ULF pulsations affected by the South Atlantic anomaly (SAA) in comparison to a conjugate region outside. Wave packets in the SAA region exhibit higher amplitudes than the pulsations in the northern hemisphere. This difference is likely influenced by the north-south asymmetry of the geomagnetic field and ionospheric conductivities, which, in turn, control the standing wave structure along the field line.