Extension of the Electron Density Enhancement From Middle to High Latitudes Observed by Swarm-A in Summer of the Southern Hemisphere

The major causal mechanism for the eastward contraction of the electron density (Ne) enhancement associated with the southern Midlatitude Summer Nighttime Anomaly (MSNA) was attributed to the thermospheric neutral wind at the middle geomagnetic latitude in the fixed local time coordinate. In the study, the Ne and horizontal cross-track ion drifts observed by the Swarm-A satellite at 462 km altitude show that the horizontal drifts can drive the Ne enhancement of the southern MSNA in the local summer of the Southern Hemisphere. Both the eastward and westward ion drifts transport the enhancement from the middle to the high geomagnetic latitudes, which results in the enhancement evolving at all the longitudes in the whole day.