Climatology of Dayside E-region Zonal Neutral Wind Shears from ICON-MIGHTI Observations

The large vertical shears in the E-region neutral zonal winds can lead to ion convergences and contribute to the plasma bubbles, but climatological studies of vertical shears of horizontal winds in a global scale are lacking due to the limitations of data coverage. Ionospheric Connection Explorer (ICON) Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) has provided neutral wind observations with unprecedented spatial coverage. In this study, the climatology of dayside E-region neutral wind shears has been examined using two-years of data (2020-2021) and we focus on the wind shears with magnitude large than 20m/s/km, since the large wind shears are more likely to cause significant perturbation in the ionosphere-thermosphere (I-T) system. The analysis shows that the occurrence probability of large shears (shears>20m/s/km) is strongly dependent on altitude, with the vertical profile varying with shear direction, latitude, season, and Local Time. In general, below 110 km altitude, large negative shears are most likely to happen during summer at 9-11 LT in 25^°N-40^°N latitudes, showing a large probability across nearly all longitudes. Meanwhile, large positive shears tend to occur in 10°S-15°N latitudes, with considerable peak probabilities exhibiting consistent longitudinal structures throughout different seasons and LT. The discrepancies between positive and negative large shears underlie different global tide dominance. The large-shear occurrences decrease dramatically above 110 km, except for an unusual enhancement observed above 110 km in latitudes ranging from 25°N-40°N during Fall and Winter in positive shears.