The correlation between equatorial electrojet and equatorial ionisation anomaly over the East African region during the solar minimum period 2008-2009

Abstract

This study analyzed the correlation between the equatorial electrojet (EEJ) and the occurrence of equatorial ionisation anomaly (EIA) over the East African region. The study was carried out during both geomagnetically quiet and disturbed conditions when Kp index values were < 2+ and > 5+, respectively. The EEJ data were obtained using a pair of magnetometers located at Adis Ababa (geographic 9.04°N, 38.77°E, geomagnetic 0.17°N, 110.47°E) and Adigrat (geographic 14.281°N, 39.46°E, geomagnetic 6.0°N, 111.06°E), both in Ethiopia while the EIA data were derived from the total electron content (TEC) data that were obtained using a set of Global Navigation Satellite System (GNSS) receivers within the East African region. The data used were for the years 2008 and 2009. The TEC data over the crest of EIA were divided by those over the trough to quantify EIA strength over the region. The EEJ intensity was estimated from the difference in the horizontal component of the geomagnetic field observed by the pair of magnetometers. The results during quiet geomagnetic conditions showed that peak values of EEJ which range from 48nT - 110nT occurred between 10:00 and 14:00 LT. The EIA’s peak which varies from 1.20 to 1.45 occurs between 20:00 to 22:00 LT. The correlation coefficients were found to vary from moderate (0.58) to strongest (0.74). During geomagnetically disturbed conditions, the correlation coefficient ranges from 0.28 to 0.45. The increased eastward electric field and photo-ionization on TEC are responsible for the strong link between EEJ and EIA. This study reveals the trend in the variation of the strength of EEJ and EIA over the East African region which can be used as a basis for developing regional models to forecast or nowcast scintillations and the ionospheric space weather prediction over this region