Unresolved Questions in Subauroral Science: Exploring Key Challenges in Physics and Chemistry

Abstract The subauroral region, located equatorward of the auroral oval, is a highly dynamic and complex interface between the magnetosphere, ionosphere, and thermosphere. While traditionally associated with stable optical structures such as stable auroral red arcs, recent observations have revealed a wide range of transient and extreme phenomena—such as subauroral ion drifts and strong thermal emission velocity enhancement—which highlight the region’s variability and intense coupling. The dynamics of the subauroral ionosphere are not only influenced by processes occurring at higher latitudes within the auroral oval but are also shaped by interactions across multiple regions of geospace, including the inner magnetosphere, ring current, inner plasma sheet, and the lower-altitude thermosphere. This growing body of research has underscored both the scientific richness of the subauroral region and the many outstanding questions regarding its drivers and chemical processes. In this paper, we present a in-depth review of observed subauroral structures, available ground-based and satellite datasets, and current modeling efforts aimed at understanding the region’s dynamics. We also examine the state of knowledge surrounding the subauroral ionospheric/thermospheric chemistry and outline critical gaps that require further investigation. Finally, we discuss the pressing need for targeted experiments and new space missions to advance our understanding of this key geospace region.