Temporal characteristics of the Equatorial Electrojet and Counter Electrojet over Ethiopian sector

Abstract

In this paper, we reported on a case study of the temporal characteristics of the Equatorial Electrojet (EEJ) and Counter Electrojet (CEJ) over Ethiopian sector during an interval on August 27, 2008 inferred from ground-based magnetometer observations. The EEJ is an intense eastward flowing electric current on the dayside along the dip equator in the equatorial ionospheric E-region between about 90–120km. This intense current has an associated magnetic field ΔH which can produce a large enhancement on the horizontal component of the geomagnetic field. Calculating the difference between the horizontal components of magnetic perturbation (H) at the equator and off the equator, ΔH, yields information about the strength of the EEJ current. Simultaneously, the sign of the current provides us with information on the direction of current flow (when the normal eastward flow of the EEJ is reversed, the resulting current is known as the CEJ). By using data collected during an interval on August 27, 2008 from Addis Ababa, Ethiopia, observatory in conjunction with Adigrat, Ethiopia, observatory and applying the above mentioned technique, we have observed the electrojet as well as the CEJ in the sector. The electrojet has been observed between about 09:15–14:30LT (LT: local time). The electrojet and CEJ are peaked at about 12:00 and 08:00LT, respectively. In addition, we have also observed the CEJ between about 09:00–09:15LT and in the afternoon about 14:00LT. This study also presents the temporal and diurnal variations of the field on different quiet and disturbed days during an interval from September 01–19, 2008. Strongly perturbed, dimly perturbed, and almost smooth variations on the fields are observed. For example, strongly perturbed fields are observed on September 03–04, 2008 and September 15, 2008 days and smooth curves are observed between September 11–14, 2008 and September 17, 2008.