West wall structuring of equatorial plasma bubbles simulated by three‐dimensional HIRB model

Abstract

AbstractPlasma density depletions in the equatorial ionosphere, or so‐called equatorial plasma bubbles (EPBs), are generated in the postsunset period and tend to have a very complex spatial structure. Especially, the east‐west asymmetry of EPBs has been reported by various observations. Using a high‐resolution bubble (HIRB) model, which is a newly developed three‐dimensional numerical model for the equatorial ionosphere, small‐scale structuring at the west wall of large‐scale F layer upwelling is clearly reproduced for the first time. It is not an eastward neutral wind but a vertical shear of zonal plasma drift velocity at the bottomside of the F region that plays an important role in accelerating the instability growth at the west wall and generating the east‐west asymmetry of EPBs.