Formation of the Bubble-Like Ionospheric Super-Depletion Structure (BLISS): MAGE Simulation of the September, 2017 Storm

This study investigates the formation of a newly identified storm-time ionospheric phenomenon, the bubble-like ionospheric super-depletion structure (BLISS) in F-region plasma densities. The observed BLISS initiates from the magnetic dip equator in the post-sunset region and expands westward and poleward, reaching midlatitudes of ∼40°, which is distinct from equatorial plasma bubbles. The mechanism of BLISS formation remains unclear. To systematically study the driving processes for this phenomenon, we employ the Multiscale Atmosphere Geospace Environment (MAGE) model that fully couples the magnetosphere, ionosphere and thermosphere models. Our MAGE simulation successfully reproduced the observed BLISS event during the 8 September 2017 storm. It shows that the depletion is caused by the vertical E × B transport as it expands westward and poleward toward midlatitudes. Numerical experiments demonstrate that sudden enhancements in southward solar wind Bz induce strong prompt eastward penetration electric fields, which are the primary cause of the BLISS and its expansion.