Quantifying Day-To-Day Variability of the Ionosphere and Thermosphere Induced by Upward Propagating Migrating Diurnal and Semidiurnal Tides

JGR - Space Physics:  The ionosphere and thermosphere (I-T) system varies significantly from one day to the next. The day-to-day variability can be driven by the lower atmospheric waves (i.e., those generated by weather systems), and the magnetosphere from above. In this paper, we use a whole atmosphere model, the Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM-X), to investigate the role of upward propagating migrating diurnal and semidiurnal tides on the day-to-day variability in the I-T system. The simulations show that the migrating tides first cause the changes in temperature and circulation in the lower thermosphere. The tidal effects subsequently propagate upward and enhance the day-to-day variabilities in both ionospheric total electron content and thermospheric composition. We also analyze the altitudinal distribution of tidally induced variations in neutral wind and find that there are wave-like structures in the variations of neutral winds in the lower thermosphere, but the structures are smoothed out by viscosity in the upper thermosphere. We also find a weaker day-to-day variability in the thermosphere than in the ionosphere due to the longer time scales of molecular diffusion and vertical advection in the thermosphere than the electrodynamic processes in the ionosphere.