Characterizing Evening Solar Terminator Waves in ICON/MIGHTI Neutral Winds

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 meridional wind signatures. Seasonal analysis reveals STWs are most prominent during solstices, when they intersect the ST about $\sim20^\circ$ from the equator in the winter hemisphere and are inclined at a $\sim40^\circ$ 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.