Planetary wave (PW) generation in the thermosphere driven by the PW-modulated tidal spectrum

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Thursday, July 16, 2020

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 modication 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; +/-75deg) due to wave-wave interactions of up to 10 m/s/day 22 and 8 K/day, 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 m/s, 5-15 m/s 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 m/s, 3-12 m/s and 4-12 K Q6DW amplitudes calculated with lower-boundary forcing of the Q6DW also included. The proposed two-stage interaction plausibly impacts quasi 2-day, 10-day and 16 day waves wind structures in the dynamo region, and thus how PW in general participate in atmosphere-ionosphere coupling.

Graphic image of Q6DW zonal wind amplitudes
Height vs. latitude structures of Q6DW zonal wind amplitudes obtained by fitting TIE-GCM hourly data within a 12-day window centered on DOY 275 for various forcings at the lower boundary of the TIE-GCM: (a) full TIME-GCM/MERRA2009 forcing; (b) “tides only” forcing ; and © planetary wave 2-7 day forcing only.

Publication: JGR Space Physics
First HAO Author: Astrid Maute

Published link: Forbes, J. M., Zhang, X., & Maute, A. 2020, Planetary wave (PW) generation in the thermosphere driven by the PW‐modulated tidal spectrum. Journal of Geophysical Research: Space Physics, 125, e2019JA027704—