Modeling of multiple effects of atmospheric tides on the ionosphere: An examination of possible coupling mechanisms responsible for the longitudinal structure of the equatorial ionosphere

A number of recent studies have highlighted the observational evidence for a coupling between atmospheric tides in the thermosphere and the electron density structure of the ionosphere. The most commonly proposed mechanism to explain this is an electrodynamic coupling between tides at E region altitudes and ion drifts at F region altitudes. However, based on both the observational evidence from recent satellite missions such as those of the neutral winds associated with nonmigrating tides at F region altitudes, and considering the theoretical effects of atmospheric tides on the thermosphere and ionosphere, more than one coupling mechanism must be considered. We use Sami2 is Another Model of the Ionosphere to test a set of electrodynamic and chemical-dynamical coupling mechanisms that could explain the link between tides in the thermosphere and the low-latitude ionosphere. We investigate the possible role of the vertical drifts during the both the day and around sunset, perturbations to the thermospheric neutral density and thermospheric [O]/[N-2], and tidal winds at F region altitudes. These simulations give an estimate of the sensitivity of the nighttime ionosphere to each of these coupling mechanisms. We then compare the results of these sensitivity tests with the effects of atmospheric tides on different thermospheric parameters as simulated by a self-consistent model of the atmosphere-ionosphere-electrodynamic system (thermosphere-ionosphere-mesosphere-electrodynamics general circulation model). This comparison shows that in addition to the E region dynamo modulation, the potential coupling between tides and the ionosphere via changes in thermospheric [O]/[N-2], meridional winds at F region altitudes, and modification of the vertical drifts around sunset could play an important role and all require further study, both with models and new observations.