Abstract
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 18-1 hour local times.