Jiyao Xu

and 5 more

In this paper, multi-ground-based instruments, including an all-sky airglow imager (ASAI), a very high frequency (VHF) radar, and eight digisondes, were combined to investigate multi-source perturbations in the evolution of an EPB event that occurred over low latitudes in China. We found this EPB event initially evolved from the bottom-type structures, most likely seeded by the atmospheric gravity wave (AGW) and the collisional shear-type instability (CSI)-inducing perturbations. Once formed, those bottom-type structures further evolved into bifurcated/plume-like structures at the ionospheric topside by the generalized Rayleigh-Taylor instability (RTI). Observed and analyzed are two different perturbation mechanisms of RTIs: one is the prereversal enhancement of the zonal electric field (PRE) inducing-RTI; another is the equatorward wind-inducing RTI around midnight. Accompanied by the PRE-inducing RTI are bifurcated/plume-like structures with a larger poleward (upward) velocity. The PRE could directly elevate the bottom-type structures to the ionospheric topside where the bifurcated/plume-like structures were generated by the RTI process. The near-midnight RTI was trigged by a vertical upward plasma jet caused by a seasonal equatorward wind in a region far away 10°N (20°N) from the geomagnetic (geographic) equator. This equatorward wind-inducing RTI persistently forced topside structures of those developed depletions to form secondary bifurcated/plume-like structures near midnight. Poleward developments of two cluster-type depletions of the EPB event were modulated by a large-scale wave-like structure (LSWS) occurring on the bottomside of the ionosphere. An eastward/westward polarization electric field inside the upwelling/trough region of the LSWS could accelerate/suppress the development of cluster-type depletions.