A simulation study on the impact of altitudinal dependent vertical plasma drift on the equatorial ionosphere in the evening

Abstract

We carry out a simulation study on the impact of altitudinal dependent plasma drift on the equatorial ionosphere in the evening, under geomagnetically quiet conditions. Our study used the vertical plasma drift velocity data measured by an incoherent scatter radar at Jicamarca (11.95°S, 76.87°W). The data covered the local sunset period on 15 and 16 November 2004. The plasma drift had significant altitudinal variations in the vertical component, which is perpendicular to the magnetic field. We employed SAMI2 (SAMI2 is another model of the ionosphere) to evaluate the effect of the altitude-dependent ion drift on the equatorial ionosphere. Three types of plasma drift velocity inputs were used in our simulations. The first input is calculated from an empirical model, the second is a height-averaged drift obtained from the observed drift velocity, and the third one corresponds to the observed altitudinal dependent drift data. A strong equatorial ionization anomaly occurred in the results of all numerical experiments. Additional layers (F3 layers) in electron densities over the equatorial F region and "arch" latitudinal structures extending to lower middle latitudes were seen in the simulations driven by the observed altitudinal dependent drift. We further show that neutral winds do not have a significant effect on the simulated F3 layers. The results of our numerical experiments suggest that the simulated additional ionospheric layers and arch structures are associated with the altitudinal gradients in the vertical plasma drift velocity.