Abstract Using the high spatial‐temporal resolution electron density profiles observed by the newly built Sanya Incoherent Scatter Radar at Sanya (18.3°N, 109.6°E) in its first 1‐month‐long continuous run with Barker code, we identified a substantial ionospheric pre‐sunrise uplift at low latitudes associated with the upward movement of ions. The uplift mainly occurs during local solar time 01:00–06:00 and is ∼52–240 km with significant night‐to‐night variability. With increasing geomagnetic and/or interplanetary activity, the uplift can have a larger amplitude. Further TIEGCM simulations show that the pre‐sunrise ionospheric uplift is jointly determined by the net effect of ambipolar diffusion, neutral wind, and E × B drift. The neutral wind during 00:00–05:00 usually lifts the ionosphere through equatorward wind. After 02:00, the weakening and/or even the reversal of downward E × B drift, which is not sufficient to offset the net uplift effect of wind and diffusion combination, triggers uplifting.
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