Tidal Control of Equatorial Vertical E × B Drift Under Solar Minimum Conditions

Observations show that equatorial ionospheric vertical drifts during solar minimum differ from the climatology between late afternoon and midnight. By analyzing WACCM-X simulations, which reproduce this solar cycle dependence, we show that the interplay of the dominant migrating tides, their propagating and in situ forced components, and their solar cycle dependence impact the F-region wind dynamo. In particular, the amplitude and phase of the propagating migrating semidiurnal tide (SW2) in the F-region plays a key role. Under solar minimum conditions, the SW2 tide propagate to and beyond the F-region in the winter hemisphere, and consequently its zonal wind amplitude in the F-region is much stronger than that under solar maximum conditions. Furthermore, its phase shift leads to a strong eastward wind perturbation near local midnight. This in turn drives a F-region dynamo with an equatorial upward drift between 18 and 1 hr local times.