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Abstract Recent observations enabled by improvements in geospace remote‐sensing instrumentation have revealed the spatial structure of continuum emissions that appear to be associated with the aurora, but little is known about the formation and drivers of these structures. We perform the first comprehensive statistical study of 52 auroral continuum structures identified using the Transition Region Explorer (TREx) network of broadband color all‐sky imagers and meridian imaging spectrographs. Superposed epoch analyses of global geomagnetic conditions reveal storm‐level activity and show that these structures appear statistically during the peak of geomagnetic disturbances. On average, the disturbance storm‐time index (Dst) decreases by approximately 50 nT to moderate storm levels in the 30 hr preceding emission observation, while the planetaryK(K_p) index rises from roughly 2 to 4.5. TREx optical data reveal a sharply peaked, spectrally “gray” luminosity that exceeds that of the surrounding aurora. The TREx auroral transport model indicates a surge of precipitating electron energy flux of approximately 5 erg/cm²/s spatially coincident with the structures themselves. A multi‐imager case study indicates that this enhancement is a coherent mesoscale region that tracks the visible structure. These results demonstrate that active geomagnetic conditions support the formation of these structures and suggest a direct coupling to energetic electron precipitation. Simultaneous observation of a broadband continuum enhancement with enhanced precipitation may favor a chemiluminescent nitric‐oxide continuum generation mechanism, although uncertainties remain regarding the viability of this mechanism. 

Abstract Geomagnetic storms transfer massive amounts of energy from the sun to geospace. Some of that energy is dissipated in the ionosphere as energetic particles precipitate and transfer their energy to the atmosphere, creating the aurora. We used the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mosaic of all‐sky‐imagers across Canada and Alaska to measure the amount of energy flux deposited into the ionosphere via auroral precipitation during the 2013 March 17 storm. We determined the time‐dependent percent of the total energy flux that is contributed by meso‐scale (<500 km wide) auroral features, discovering they contribute up to 80% during the sudden storm commencement (SSC) and >∼40% throughout the main phase, indicating meso‐scale dynamics are important aspects of a geomagnetic storm. We found that average conductance was higher north of 65° until SYM‐H reached −40 nT. We also found that the median conductance was higher in the post‐midnight sector during the SSC, though localized conductance peaks (sometimes >75 mho) were much higher in the pre‐midnight sector throughout. We related the post‐midnight/pre‐dawn conductance to other recent findings regarding meso‐scale dynamics in the literature. We found sharp conductance peaks and gradients in both time and space related to meso‐scale aurora. Data processing included a new moonlight removal algorithm and cross‐instrument calibration with a meridian scanning photometer and a standard photometer. We compared ASI results to Poker Flat Incoherent Scatter Radar (PFISR) observations, finding energy flux, mean energy, and Hall conductance were highly correlated, moderately correlated, and highly correlated, respectively. 

Abstract Strong Thermal Emission Velocity Enhancement (STEVE), is a captivating optical phenomenon typically observed in the mid‐latitude ionosphere. This paper presents an intriguing observation of a STEVE event at high‐latitudes, approximately 10 degrees poleward of previously documented observations. This event was recorded in Yellowknife, Canada, by a TREx RGB imager and a citizen scientist. Swarm satellites traversed the latitude of the observation, measuring extreme westwards ion drift velocities exceeding 4 km/s. Such velocities are more typically associated with the subauroral region located at mid‐latitudes, rather than at the high‐latitudes reported here. Significantly, this event occurred without a substorm, which differs from previous STEVE observations. While high‐latitude radars detected fast ionospheric equatorward flows, GOES satellite did not record any injections. These observations suggest that the inner magnetosphere is highly inflated. This unique case study raises new questions surrounding subauroral dynamics and the influence of magnetospheric configurations on ionospheric responses.