INVESTIGATION ON LONGITUDINAL AND DECADAL VARIATIONS OF THE EQUATORIAL ELECTROJET USING A PHYSICAL MODEL

Abstract:

Although several aspects of equatorial electrojet (EEJ) have been addressed in the past, not much attention is paid to critically investigate characteristic changes of EEJ with longitude and on a decadal time scale. A detailed investigation in this regard is carried out using a physical model (Anandarao, GRL, 1976) of electrojet. The general characteristics (amplitude, width, peak altitude) of EEJ are obtained for different longitudes along with the changes over the past seven decades. A few important aspects that came out from this investigation include (i) change in the half-width of EEJ longitude and reason for these differences, (ii) changes in EEJ strength over time scale of 1960-2020 in steps of a decade, (iii) wave-4 structure in the EEJ current density and integrated EEJ current. Dependence of EEJ current density on the geomagnetic field is brought out. In addition, empirical relationships of the peak EEJ current density and integrated EEJ current with ionospheric parameters and geomagnetic field strengths are brought out. Therefore, this investigation provides a comprehensive account of the longitudinal and decadal variations of EEJ that can be used in observational and modelling studies to understand the low-latitude ionospheric electrodynamics in greater detail.