Some modelling studies of the equatorial ionosphere using the Sheffield University Plasmasphere Ionosphere Model

Abstract

The Sheffield University Plasmasphere Ionosphere Model (SUPIM) has been used to study the importance of diffusion, vertical E × B drift, and neutral wind on the generation and modulation of the equatorial plasma fountain and the equatorial anomaly of the Earth's ionosphere. The study has been carried out for the longitude of Jicamarca under magnetically quiet equinoctial conditions at medium solar activity. The model results indicate that the behaviour of the fountain closely follows the variation of the F region vertical E × B drift. During daytime the fountain rises to a maximum altitude of about 800 km at the equator and covers magnetic latitudes of about ±30°. At regions outside the fountain plasma flows towards the equator and this leads to the formation of an additional layer during the prenoon hours between latitudes ±10°; we call this layer the G layer. The maximum plasma concentration of the G-layer can be greater than that of the F layer for a short period of time just before noon. In the evening, soon after the drift turns downward, the fountain becomes a reverse fountain with supply of ionization from the region outside the fountain. The neutral wind modulates and introduces latitudinal asymmetries into both the fountain and anomaly.