Changes of thermospheric composition and ionospheric density caused by quasi 2-day wave dissipation

Using the thermosphere-ionosphere-mesosphere electrodynamics-general circulation model, we investigate the effect of quasi 2-day wave (QTDW) dissipation on thermospheric composition (O/N₂) and ionospheric electron density during solar minimum. The overall thermospheric and ionospheric changes induced by the QTDW are evaluated by running the model with and without QTDW forcing imposed at the model lower boundary. The dissipation of the westward propagating QTDW in the lower thermosphere causes westward mean wind acceleration and drives a poleward meridional circulation. The circulation induced by the QTDW, as determined by the difference between the mean wind patterns of a run with the QTDW and a base run without the QTDW, enhances the mixing of constituents in the lower thermosphere. Through molecular diffusion, the decrease of the O mixing ratio and the increase of the N₂ and O₂ mixing ratios propagate from the lower thermosphere into the upper thermosphere. As a result, the O/N₂ ratio near the ionospheric F₂ peak is reduced by about 16-20% at low and midlatitudes. This in turn produces an approximately 16-32% depletion in the F₂ peak electron density at low and midlatitudes. The simulated decrease of electron density during a QTDW event is in quantitative agreement with published observations. This work suggests a new major pathway for the traveling planetary wave from the lower atmosphere to affect the thermosphere and ionosphere via dissipation and mean wind acceleration. Key Points The dissipation of QTDW drives a meridional circulation The extra circulation enhances the mixing and changes the O/N₂ The reduced O/N₂ leads to the reduction of ionospheric electron density