Journal cover Journal topic
Annales Geophysicae Sun, Earth, planets, and planetary systems An interactive open-access journal of the European Geosciences Union
Ann. Geophys., 36, 841-853, 2018
https://doi.org/10.5194/angeo-36-841-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Regular paper
13 Jun 2018
Statistical analysis of the correlation between the equatorial electrojet and the occurrence of the equatorial ionisation anomaly over the East African sector
Patrick Mungufeni1, John Bosco Habarulema2,3, Yenca Migoya-Orué4, and Edward Jurua1 1Mbarara University of Science and Technology, P.O. Box 1410 Mbarara, Uganda
2South African National Space Agency (SANSA) Space Science, Hermanus 7200, South Africa
3Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa
4T/ICT4D laboratory of the Abdus Salam International Center for Theoretical Physics, 34151 Trieste, Italy
Abstract. This study presents statistical quantification of the correlation between the equatorial electrojet (EEJ) and the occurrence of the equatorial ionisation anomaly (EIA) over the East African sector. The data used were for quiet geomagnetic conditions (Kp  ≤  3) during the period 2011–2013. The horizontal components, H, of geomagnetic fields measured by magnetometers located at Addis Ababa, Ethiopia (dip lat.  ∼ 1° N), and Adigrat, Ethiopia (dip lat.  ∼ 6° N), were used to determine the EEJ using differential techniques. The total electron content (TEC) derived from Global Navigation Satellite System (GNSS) signals using 19 receivers located along the 30–40° longitude sector was used to determine the EIA strengths over the region. This was done by determining the ratio of TEC over the crest to that over the trough, denoted as the CT : TEC ratio. This technique necessitated characterisation of the morphology of the EIA over the region. We found that the trough lies slightly south of the magnetic equator (0–4° S). This slight southward shift of the EIA trough might be due to the fact that over the East African region, the general centre of the EEJ is also shifted slightly south of the magnetic equator. For the first time over the East African sector, we determined a threshold daytime EEJ strength of  ∼  40 nT that is mostly associated with prominent EIA occurrence during a high solar activity period. The study also revealed that there is a positive correlation between daytime EEJ and EIA strengths, with a strong positive correlation occurring during the period 13:00–15:00 LT.
Citation: Mungufeni, P., Habarulema, J. B., Migoya-Orué, Y., and Jurua, E.: Statistical analysis of the correlation between the equatorial electrojet and the occurrence of the equatorial ionisation anomaly over the East African sector, Ann. Geophys., 36, 841-853, https://doi.org/10.5194/angeo-36-841-2018, 2018.
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Short summary
We have established that, over the East African region, the trough of the equatorial ionisation anomaly (EIA) during high solar activity and quiet geomagnetic conditions lies slightly south of the magnetic equator. During the equinox and December solstice seasons, and a local time interval of 13:00–15:00, the probability of observing the EIA on days with daytime equatorial electrojet (EEJ) strength ≥ 40 nT was mostly > 80 %.
We have established that, over the East African region, the trough of the equatorial ionisation...
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