Analysis of the Spatio-Temporal Variability of the Solar Quiet Sq/Sr Ionospheric Currents of the Equatorial EEJ and CEJ/REJ Electrojets by the Ionization Densification Surface

Abstract

The objective of this article was to analyze the spatiotemporal variability of ionospheric currents, specifically Solar Quiet Sq/Sr, equatorial electrojets (EEJ), and counter-electrojets (CEJ/REJ), across the ionization density surface. The findings, based on the observations of two cities—Singapore (1.28˚N, 103.85˚E) and Bobo-Dioulasso (Guiriko) (11.11˚N, 4.28˚W)—reveal that the power and electron density of the ionization density surface are lower at latitudes closer to the equator than at increasingly distant latitudes. This highlights, on the one hand, the equatorial ionization anomaly and, on the other hand, the very high velocity of electric particles at the equator due to the amplification of the Sq current density observed there. Furthermore, the electric field deduced from the equality of ionospheric power density and the magnitude of the Poynting vector, appearing very weak at the equator, thus confirms the very high electrical conductivity of the Sq currents observed at the equator. Subsequent analysis of the densification surface trajectory shows that the plasma flow movement is twisted and maintains a counterclockwise direction in the Northern Hemisphere and a clockwise direction in the Southern Hemisphere. At latitudes very close to the equator, the overall movement of the two plasma flows indicates, firstly, that the magnetic field cannot be entirely oriented towards the North, and secondly, that the electric field vector is neither horizontal nor vertical, thus suggesting the unlikely existence of an equatorial electrojet. However, by solving a fundamental equation that takes into account magnetic declination, and using the Ey component of the electric field, areas with a strong propensity for the formation of EEJs and CEJs will be identified. Thus, for the city of Singapore, EEJ (in the sense of Ey oriented from west to east) will be mainly observed during the hours of vertical drift (3 p.m. and 9 p.m.), while CEJ (in the sense of Ey oriented from east to west) will be observed during the hours of production (3 a.m., 9 a.m. and 12 p.m.) and respectively the reverse for the city of Bobo-Dioulasso. Finally, the analysis shows that equatorial electrojets and counter-electrojets are simply Sq currents amplified by the production factor and therefore of the same nature as Sq.