Zonally symmetric oscillations of the thermosphere at planetary wave periods

First, it is demonstrated that a tidal spectrum modulated at PW periods (3-20days) entering the ionosphere-thermosphere system near 100km is responsible for producing +/- 40m/s and +/- 10-15K PW period oscillations between 110 and 150km at low to middle latitudes.

The dominant response is broadband and zonally symmetric (i.e.,"S0") over a range of periods and is attributable to tidal dissipation; essentially, the ionosphere-thermosphere system vacillates in response to dissipation of the PW-modulated tidal spectrum. In addition, some specific westward propagating PWs such as the quasi-6-day wave are amplified by the presence of the tidal spectrum; the underlying mechanism is hypothesized to be a second-stage nonlinear interaction.