Study of the equatorial electrojet starting from the electrodynamics parameters of the equatorial ionosphere

Abstract The determination of the physical parameters of the equatorial electrojet (EEJ) from Korhogo (Latitude +9.3; Longitude -5.4; Dip -0.67) during the period of 1993 to 1994 was carried out by data of ionosonde IPS-42. The results made it possible to show that for a low average value of electron drift vertical approximately 5 m/s to the solstices and 6 m/s with the equinoxes in the morning, we obtained around midday a strong density of current of the EEJ (3.30A/km 2 in 1993 and 2.6A/km 2 in 1994). We determined during this study the values of the various electric fields intervening in the mechanism of formation of the EEJ. We showed the strong contribution of the polarization electric field in this phenomenon. The results gave the values of the zonal and polarization electric fields respectively 0.19mV/m and 3.5mV/m. The data of ionosonde IPS-42 made it possible to determine the density and intensity of current center of the EEJ (I 0 =231.11±53.7 A/km). We compared the intensity of the current in the center obtained with the ionosonde with that of the data on the ground. We obtained appreciably similar results

Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

International audienceIn this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5° W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north–south (Ex) and east–west (Ey) components of telluric electric field were analyzed, along with that of the three components (H,  D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of −110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are Ex =  520 mV km−1 and Ey =  400 mV km−1. The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are Ex =  550 mV km−1 and Ey =  340 mV km−1. Note that the sfe impact on the geo-electric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13° N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt