Storm‐Time Coupling of Equatorial Nighttime F Region Neutral Winds and Plasma Drifts

We used observations from the Peruvian Fabry‐Perot Interferometer network and from the Jicamarca radar to study the coupling of equatorial nighttime thermospheric winds and ionospheric drifts under moderate solar flux conditions. We show that the coupling of the extended quiet time zonal winds and drifts increases from dusk to midnight and is stronger during equinox than during June solstice. After midnight, they are strongly coupled, except during December solstice when the drifts are stronger. The nighttime disturbance zonal winds and drifts, derived by removing the corresponding quiet time values, are westward with peak magnitudes around midnight. They are in close agreement, except at early night when the winds are stronger, and have strongest (weakest) magnitudes during equinox (June solstice). We also present observations showing the strong neutral wind‐plasma drift coupling during the September 2017 and August 2015 large geomagnetic storms. We show that during the early phase of the September 2017 storm there were large and short‐lived, prompt penetration electric field‐driven, correlated oscillations (~1 hr) in the vertical and zonal plasma drifts, and in the zonal and meridional winds. These are the first observations of prompt penetration‐driven equatorial zonal and meridional wind disturbances. In this event, the vertical and zonal drift oscillations were anticorrelated, and the zonal winds followed the zonal drift oscillations with a delay of ~15 min. Our results illustrate the strong coupling of equatorial thermospheric winds and plasma drifts during geomagnetically quiet as well as during short‐lived prompt penetration and long‐lasting disturbance dynamo events.