Neutral wind and plasma drift effects on low and middle latitude total electron content

Abstract

A physics‐based numerical ionosphere/plasmasphere model (IPM) was used to study the effects of daytime neutral wind and electric field perturbations on the subsequent evolution of the afternoon and postsunset total electron content (TEC) during vernal equinox conditions. The model solves the transport equations for six ions on convecting flux tubes that realistically follow the geomagnetic field. The IPM covers geomagnetic latitudes from about 60°N to 60°S and equatorial crossing altitudes from 90 to 30,000 km. Two of the input parameters required by the IPM are the thermospheric neutral wind and the low‐latitude electric field, which can be provided by existing empirical models or externally specified. To study effects of the neutral winds and the electric fields on TEC, these two model inputs were externally modified, and the resulting TEC variations were compared. Neutral wind and electric field modifications were introduced at three different local times in order to investigate the effect of different perturbation times on the evolution of TEC. Three longitudes (78°E, 273°E, and 318°E) were considered, and the results correspond to conditions of medium solar activity and low geomagnetic activity. The largest TEC changes were found predominantly in the equatorial anomaly, and a significant longitudinal dependence was observed. The simulation results indicate that TEC variations at 2100 LT vary nonlinearly at low latitudes and linearly at middle latitudes with the elapsed time after the imposed perturbations. An important outcome of this study is that daytime neutral wind and/or electric field modifications can lead to essentially identical TEC changes at 2100 LT.