Seasonal Variability of the DE3 and DE2 Non-Migrating Tides in Middle Thermospheric Temperature and Composition during October 2018–August 2021 as Revealed by GOLD

The longitudinal/local time response of the thermosphere-ionosphere to lower atmospheric conditions is controlled in large part by upward propagating non-migrating tides. The diurnal eastward propagating tides with zonal wavenumbers 3 and 2 (DE3 and DE2, respectively) are associated with the widely documented 4-peak and 3-peak longitudinal variations at low latitudes. Excited by persistent tropical rainfall, these tides reach their strongest amplitudes in the mesosphere/lower thermosphere where they modulate the ionospheric E-region dynamo. Observations of tides in the middle thermosphere (~120-250 km) are limited, especially in temperature and composition. A recently developed approach makes possible the estimation of the strongest non-migrating tides using observations of column-integrated disk neutral temperature and O/N2 from NASA’s Global-scale Observations of the Limb and Disk (GOLD) Mission. Here, GOLD observations are used to diagnose the seasonal variability of DE3 and DE2 in this poorly characterized altitude region. To determine whether the middle thermospheric tides correlate with upward propagating tides in the MLT, we compare tidal amplitudes derived from GOLD with those simulated by the TIE-GCM, Hough Mode Extension tides derived from ICON winds and temperatures in the MLT region, and those derived from nitric oxide cooling rates observed by SABER onboard TIMED.