Multi-source Perturbations in the Evolution of a Low-latitudinal
Equatorial Plasma Bubble Event Occurred over China
Abstract
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.