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Abstract The prereversal enhancement (PRE) is a brief surge in upward plasma velocity in the evening equatorial ionosphere and a driver of equatorial spread‐F. This study reports the first PRE climatology from Ionospheric Connection Explorer (ICON) data, exhibiting seasonal and longitudinal variability that is qualitatively consistent with results from two previous satellite missions. Previous missions, however, lacked the neutral wind observations to characterize their impact on the PRE. To quantitatively assess wind impacts, numerical experiments are performed with a standalone dynamo solver using winds from the TIEGCM‐ICON, which is driven from below by observed tides. To quantify the impact of solar/magnetic geometry, such as the alignment between the solar terminator and the magnetic meridian, the model was first driven with seasonally and longitudinally averaged winds (which includes seasonally averaged zonal‐mean winds and migrating tides). This reproduces the observed PRE variability with a correlation of 0.44. Incorporating longitudinally and seasonally varying wind patterns improves the correlation to 0.68. This suggests that climatological wind variability is an important driver of PRE variability, but future work is needed to account for the missing variability. Potential missing drivers include conductivity variability near the terminator and mesoscale wind features such as the solar terminator wave. 

Abstract Recent studies suggest that, despite its aurora‐like appearance, the picket fence may not be driven by magnetospheric particle precipitation but instead by local electric fields parallel to Earth's magnetic field. Here, we evaluate the parallel electric fields hypothesis by quantitatively comparing picket fence spectra with the emissions generated in a kinetic model driven by local parallel electric fields energizing ambient electrons in a realistic neutral atmosphere. We find that, at a typical picket fence altitude of 110 km, parallel electric fields between 40 and 70 Td (∼80–150 mV/m at 110 km) energize ambient electrons sufficiently so that, when they collide with neutrals, they reproduce the observed ratio of N₂first positive to atomic oxygen green line emissions, without producing first negative emissions. These findings establish a quantitative connection between ionospheric electrodynamics and observable picket fence emissions, offering verifiable targets for future models and experiments. 

Abstract The moving solar terminator (ST) generates atmospheric disturbances, broadly termed solar terminator waves (STWs). Despite theoretically recurring daily, STWs remain poorly understood, partially due to measurement challenges near the ST. Analyzing Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) data from NASA's Ionospheric Connection Explorer (ICON) observatory, we present observations of STW signatures in thermospheric neutral winds, including the first reported meridional wind signatures. Seasonal analysis reveals STWs are most prominent during solstices, when they intersect the ST about ∼20° latitude from the equator in the winter hemisphere and have phase fronts inclined at a ∼40° angle to the ST. We also provide the first observed STW altitude profiles, revealing large vertical wavelengths above 200 km. Comparing these observations to four different models suggests the STWs likely originate directly or indirectly from waves from below 97 km. STWs may play an under‐recognized role in the daily variability of the thermosphere‐ionosphere system, warranting further study.