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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 Model-observation comparisons of type-I X-ray bursts (XRBs) can reveal the properties of accreting neutron star systems, including the neutron star compactness. XRBs are powered by nuclear burning, and a handful of reactions have been shown to impact the model results. Reactions in the NiCu cycles, featuring a competition between⁵⁹Cu(p,γ)⁶⁰Zn and⁵⁹Cu(p,α)⁵⁶Ni, have been shown to be among the most important reactions as they are a critical checkpoint inrp-process flow and significantly impact the light curves and burst ashes. We report a direct measurement of⁵⁹Cu(p,α)⁵⁶Ni, bringing stringent constraints on this reaction rate. New results rule out a strong NiCu cycle in XRBs, with a negligible degree of recycling, ≤5% up to 1.5 GK. The new reaction rate, when varied within new uncertainty limits, shows no impact on one-zone XRB model light curves tailored for clocked-bursterGS1826–24, hence removing an important nuclear physics uncertainty in the model-observation comparison. 

Key Points Detailed analysis of spectral transition of a Stable Auroral Red (SAR) Arc into Strong Thermal Emission Velocity Enhancement (STEVE) emission Ionospheric threshold conditions may be a requirement for the evolution of STEVE Basic parameters of transition features from SAR Arc to STEVE presented