Mesoscale Auroral Dynamics in the Nightside Transition Region: A Ground-Based Study of Giant Undulations

The Nightside Transition Region (NTR)—the boundary between the outer and inner magnetosphere—plays a critical role in magnetospheric plasma dynamics. During quiet periods, it acts as a “magnetic wall,” while in active times, it becomes a site of intense plasma energization. Although the large-scale morphology of the NTR is fairly well characterized, the role of mesoscale structures within this region remains poorly understood.
Giant undulations—auroral features located at the equatorward edge of the diffuse aurora—offer a unique opportunity to probe mesoscale dynamics in the NTR. Historically, their formation and evolution have been examined using global auroral imaging, which is limited in both spatial and temporal resolution.
In this study, we leverage recent advancements in ground-based optical instrument arrays to analyze the fine-scale characteristics and temporal evolution of giant undulations. Our findings provide new insights into the generation mechanisms of these structures and their contribution to the overall dynamics of the auroral region, offering a fresh perspective on mesoscale processes in the NTR.