Disturbance Neutral Winds Effects on the Ionospheric Strip‐Like Bulge at Lower‐Middle Latitudes

Abstract

AbstractDuring the geomagnetic storm on 3–6 November 2021, the in‐situ plasma density and the gridded total electron content (TEC) maps registered a persistent presence of the strip‐like bulges (electron density enhancement, also known as the shoulders in previous literatures) at lower‐middle latitudes. The observed strip‐like bulge resided in the Pacific‐America‐Atlantic sector and lasted from 07:00 UT on 4 November to 20:00 UT on 6 November. For the first time, the temporal evolution of the 2‐D strip‐like bulge was recorded by gridded TEC maps, though observations were limited over the North American continents. The TEC maps showed a continuous shrinking of the nightside midlatitude plasma band structure right before the presence of the narrow strip‐like bulge. Simultaneous measurements from the Ionospheric Connection Explorer satellite (ICON) revealed an equatorward turning of the field‐aligned ion transportation driven by the disturbance equatorward neutral winds. However, the enhanced fountain effect at low latitudes was not observed during the entire formation phase of the strip‐like bulge. We propose that the storm‐induced enhanced equatorward thermospheric neutral winds push the plasma equatorward along the field lines, and the plasma band structure was developed into the strip‐like bulge. In addition, the ion composition of both the plasma band structure and the strip‐like bulges are dominated by H+, and the maintenance of the strip‐like bulge could be due to the compensation of the downward plasmaspheric content flux.