Investigation on longitudinal and decadal variations of the equatorial electrojet using a physical model

Abstract

A detailed investigation on longitudinal and decadal variations of general characteristics (amplitude, width, peak altitude) of the equatorial electrojet (EEJ) is carried out using a physics-based model of electrojet. A few important aspects that emerge from this investigation include (i) changes in the half-width of EEJ with longitude and it’s dependence on the rate of change of dip-angle with latitude, (ii) changes in EEJ strength as large as 10–20% over the Peruvian and Brazilian sectors from 1960 to 2020 associated with significant changes in the local geomagnetic field, (iii) wave-4 structure in the EEJ current density and integrated EEJ current. In addition, it is shown that the peak EEJ current density over different longitudes inversely depends on the strength of geomagnetic field. More importantly, relationships of EEJ parameters (such as half-width, peak current density, integrated current) with ionospheric electric field, electron density, and geomagnetic field are brought out. These relationships are verified using EEJ observations carried out earlier using sounding rocket and ground based magnetometers. This comprehensive account of the longitudinal and decadal variations of EEJ along with the expressions to calculate EEJ characteristics can be used in observational and modelling studies to understand the low-latitude ionospheric electrodynamics in greater detail.