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

Abstract

AbstractThe 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 110 km 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 (90–300 km; ±75°) due to wave‐wave interactions of up to 10 ms−1 day−1 and 8 K day−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 5–20 ms−1, 5–15 ms−1, and 5–10 K, 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 10–22 ms−1, 3–12 ms−1, and 4–12 KQ6DW 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.