Planetary Wave (PW) Generation in the Thermosphere Driven by the PW-Modulated Tidal Spectrum

The National Center for Atmospheric Research thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) is used to conduct numerical experiments that isolate and elucidate a substantial modification of the quasi-6-day wave (Q6DW) above 110km due to presence of the planetary wave (PW)-modulated tidal spectrum. A two-stage nonlinear tidal interaction is proposed, and its role in vertical coupling by the Q6DW is quantified. The theory enables calculation of net Q6DW accelerations and heating rates in the height-latitude domain (90-300km; 75 degrees) due to wave-wave interactions of up to 10ms(-1)day(-1) and 8Kday(-1), respectively. The Global-Scale Wave Model (GSMW) is used to demonstrate that these forcings produce Q6DW zonal and meridional wind amplitudes, and temperatures, of order 5-20ms(-1), 5-15ms(-1), and 5-10K, respectively. Notably, Q6DW thermal forcing in the GSWM accounts for near-doubling of the wind magnitudes calculated with momentum forcing alone. The computed values are comparable to the 10-22ms(-1), 3-12ms(-1), and 4-12KQ6DW amplitudes calculated with lower-boundary forcing of the Q6DW also included. The proposed two-stage interaction plausibly impacts other PW wind structures in the dynamo region and thus how PW in general participate in atmosphere-ionosphere coupling. Key Points Vertical penetration of the quasi-6-day wave (Q6DW) into the thermosphere is substantially modified by the PW-modulated tidal spectrum A two-stage nonlinear tidal interaction is shown to play a significant role in defining the Q6DW This result is relevant to atmosphere-ionosphere coupling by the Q6DW and likely other PW including the Q2DW, Q10DW, and Q16DW