Abstract
Abstract. In 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.
Highlights
Intense space weather events like geomagnetic storms and substorms are potential sources of electric induction within the earth
The present study analyzes geomagnetic field and geoelectric field variations observed in West Africa during the International Equatorial Electrojet Year (IEEY) campaign
The observations demonstrate that intense space weather events are potential sources of electric inductions within the Earth at low latitudes
Summary
Intense space weather events like geomagnetic storms and substorms are potential sources of electric induction within the earth. Magnetosphere–ionosphere coupling through geomagnetic field lines generates intense currents such as auroral electrojets in the high-latitude ionosphere These currents are extremely enhanced during geomagnetic storms and substorms and cause very intense geomagnetic. Ngwira et al (2013) found the largest perturbations in the geomagnetic and geo-electric fields at high latitudes and an important enhancement in the EEJ influence area. Carter et al (2015) analyzed potential induction effects of the so-called interplanetary shock events (ssc and solar flare effect, sfe) on the basis of the time derivatives of geomagnetic field variations They emphasized potential threats of important GICs during these shock events near the geomagnetic equator due to enhancements of geomagnetic disturbances caused by the EEJ in this area. Variations in the north–south (Ex) and east–west (Ey) components of telluric (geo-electric) field are 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 on 4 April 1993
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
