Quantifying Ionospheric and Thermospheric Day-to-Day Variability Due To the Upward Propagating Migrating Diurnal and Semidiurnal Tides

Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) simulations are used to investigate the thermospheric and ionospheric day-to-day variability caused by the upward propagating migrating diurnal (DW1) and semidiurnal (SW2) tides under conditions with constant solar and geomagnetic forcing. In the lower thermosphere, tidal dissipation deposits momentum and energy, causing significant variability in neutral winds and temperature of ∼20 m/s and ∼5 K for DW1, and ∼40 m/s and ∼20 K for SW2. DW1 and SW2 lead to an overall global reduction of the ratio of column integrated atomic Oxygen to molecular Nitrogen (ΣO/N₂) and an increase in ΣO/N₂ day-to-day variability. DW1 and SW2 also exert a significant impact on the equatorial electrodynamics, which leads to variations in ionospheric total electron content (TEC). The ΣO/N₂ day-to-day variability is small (∼1.5%), and DW1 and SW2 contribute ∼10% and ∼20% to this day-to-day variability. In contrast, the TEC day-to-day variability is much larger (∼20%), with DW1 and SW2 contributing ∼20% and ∼40%, respectively. The wind variations caused by DW1 and SW2 exhibit different vertical wavelengths of ∼30 and ∼60 km in the lower thermosphere, but are nearly infinite in the upper thermosphere. The large tide vertical wavelengths in the upper thermosphere are caused by dissipative processes in the thermosphere. Our results demonstrate that the effects of upward propagating DW1 and SW2 on TEC are comparable on day-to-day and seasonal scales, but for thermospheric ΣO/N₂, their impact on the day-to-day scale is significantly weaker than that on the seasonal scale.