A New Paradigm for Multi-Scale Geospace Dynamics Inspired by Recent Observations of the Substorm

Abstract:

Ground-based observations of the spatio-temporal evolution of the aurora and related processes have played a critical role in the dramatic advances in substorm research that have unfolded over the THEMIS era. For example, with its unique combination of extent of coverage, and time and space resolution, THEMIS-ASI has shown dynamics unfolding rapidly across surprisingly large distances. Its image sequences show the substorm as part of a system-level dynamic that connects the inner magnetosphere to the distant tail, and perhaps even the dayside. Together with simultaneous observations by the THEMIS spacecraft, the auroral images have also transformed our understanding of magnetic mapping during the growth phase. In this talk I will review some true science highlights that have been enabled by ground-based observations since the launch of THEMIS. I will also highlight how these ground-based observations fall short of capturing key aspects of the dynamics around expansion phase onset. This creates difficulties, for example, in understanding why, how and where dispersionless injections begin. I finish with a discussion of how ground-based observations targeting the substorm have impacted geospace research in general.