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We report a new modeling capability that self-consistently couples physics-based magnetospheric electron precipitation with its impact on the ionosphere. Specifically, the ring current model RAM-SCBE is two-way coupled to an ionospheric electron transport model GLOW (GLobal airglOW), representing a significant improvement over previous models, in which the ionosphere is either treated as a 2-D spherical boundary of the magnetosphere or is driven by empirical precipitation models that are incapable of capturing small-scale, transient variations. The new model enables us to study the impact of substorm-associated, spectrum-resolved electron precipitation on the 3-D ionosphere. We found that after each substorm injection, a high-energy tail of precipitation is produced in the dawn sector outside the plasmapause, by energetic electrons (10 < E < 100 keV) scattered by whistler-mode chorus waves. Consequently, an ionospheric sublayer characterized by enhanced Pedersen conductivity arises at unusually low altitude (similar to 85 km), with its latitudinal width of similar to 5-10 degrees in the auroral zone. The sublayer structure appears intermittently, in correlation with recurrent substorm injections. It propagates eastward from the nightside to the dayside in the same drift direction of source electrons injected from the plasma sheet, resulting in global impact within the ionosphere. This study demonstrates the model's capability of revealing complex cross-scale interactions in the geospace environment.

Plain Language Summary Understanding the variability within the near-Earth magnetosphere-ionosphere-thermosphere system is not only a scientific goal but also a critical need for reliable nowcasting and forcasting of hazardous space weather. The system is fully coupled in a variety of ways that challenge our current modeling and observational capabilities. In order to unify the ionospheric and magnetospheric dynamics and their interactions, we report a latest modeling effort that self-consistently couples the magnetospheric particle precipitation with its impact on the ionosphere. This model significantly advances the consistency of the models, providing the opportunity to study the 3-D ionospheric variability and associated transient magnetospheric drivers. With this new tool, we find that earthward particle injections in the magnetosphere result in energetic electron precipitation with 10 < E < 100 keV, which cause intense ionization and a transient sublayer with enhanced electric conductivity at unusually low altitudes near 85 km. The layer develops in a global manner that may change the traditional pattern of current closure within the geospace system. Our new model demonstrates a capability of revealing the complex cross-scale interactions within the near-Earth environment.