Self‐consistent modeling of equatorial dawn density depletions with SAMI3

Large‐scale, dawn density depletions in the equatorial ionosphere have been observed by instruments on the STPSat1 and CHAMP satellites. The Naval Research Laboratory (NRL) ionosphere model SAMI3 (Sami3 is Also a Model of the Ionosphere) is used to study this new phenomenon using a self‐consistent electric field. Two empirical Horizontal Wind Models (HWM) are used in the simulation study: HWM93 and HWM07. Dawn density depletions are found using HWM07 but not with HWM93. The cause of the depletions is a post‐midnight enhancement of the eastward electric field that generates an upward plasma drift. This drift lifts low density plasma to high altitudes (i.e., ∼600 km). We compare our model results to remote sensing data and to in situ satellite data.

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