Variations in the Ionosphere-Thermosphere System from Tides, Ultra-Fast Kelvin Waves, and Their Interactions.

Neutral winds in the lower thermosphere play an important role in determining the state of the whole ionosphere-thermosphere (I-T) system. These winds drag plasma along and across the magnetic field lines generating E-fields that produce ExB motions. The dynamic behavior in this region affects the use of radio and other technologies through modifications of the plasma at various scales. The neutral wind and temperature effects associated with the atmospheric tides are some of the most important dynamic features in the I-T system. These tidal structures transfer energy and momentum into the region from below. Outside of the atmospheric tides, there are other waves with similar spatial and temporal scales that can propagate into the I-T system, such as the ultra-fast Kelvin wave (UFKW). Wave-wave interactions between the atmospheric tides and UFKWs produce secondary waves that can themselves affect the state of the I-T system. This study examines the response of the I-T system to the atmospheric tides, a single UFKW, and their interactions using the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). We find that the larger wave-wave coupling, reported in other studies, is occurring below the mesopause and the observations by the Ionospheric Connection Explorer (ICON) mission will be able to fully capture these wave interactions by observing winds and temperatures at the mesopause and above.