Abstract
Abstract. In this paper, an empirical total electron content (TEC) model and trends in the TEC over the African low-latitude region are presented. GPS-derived TEC data from Malindi, Kenya (geographic coordinates 40.194∘ E, 2.996∘ S), and global ionospheric maps (GIMs) were used. We employed an empirical orthogonal function (EOF) analysis method together with least-squares regression to model the TEC. The EOF-based TEC model was validated through comparisons with GIMs, the GPS-derived TEC and the TEC derived from the International Reference Ionosphere 2016 (IRI-2016) model for selected quiet and storm conditions. The single-station EOF-based TEC model over Malindi satisfactorily reproduced the known diurnal, semiannual and annual variations in the TEC. Comparison of the EOF-based TEC model results with the TEC derived from the IRI-2016 model showed that the EOF-based model predicted the TEC over Malindi with fewer errors than the IRI-2016. For the selected storms, the EOF-based TEC model simulated the storm time TEC response over Malindi better than the IRI-2016. In the case of the regional model, the EOF-based TEC model was able to reproduce the TEC characteristics in the equatorial ionization anomaly region. The EOF-based TEC model was then used as a background for estimating TEC trends. A latitudinal dependence in the trends was observed over the African low-latitude region.
Highlights
The features of the low-latitude ionosphere are quite unique
To asses the performance of the empirical orthogonal function (EOF)-based total electron content (TEC) model, we compared the model results with the TEC derived from the International Reference Ionosphere (IRI)-2016 model and global ionospheric maps (GIMs) obtained from the website of the Center for Orbit Determination in Europe (CODE)
The TEC from the EOF-based TEC model will be referred to as the EOF TEC, the TEC derived from the GPS receiver in Malindi as the GPS TEC, the TEC from CODE’s GIMs as CODE’s TEC and the TEC from the IRI2016 model as the IRI TEC
Summary
The features of the low-latitude ionosphere are quite unique. During the daytime, a double-peaked ionization structure appears over the low-latitude region, a phenomenon often referred to as the equatorial ionization anomaly (EIA). Ionospheric variability over the low-latitude region of Africa, based on TEC analysis, has been reported before (e.g., Adewale et al, 2011; Olwendo et al, 2012; Habarulema et al, 2013; Andima et al, 2015) From these studies, the diurnal, seasonal, disturbed and quiet-time TEC characteristics over the region have been revealed. With a relatively longer record of data in the achieves, it is imperative to extend these studies to the long-term TEC characteristics over the African low-latitude region for practical applications. Averaging and smoothing applied when deriving the model coefficients may limit its accuracy in capturing peculiar features such as the TEC variability in the EIA region. The objective of this paper is twofold: first to attempt to model the low-latitude TEC, and second to estimate trends in the variation of the ionospheric TEC over the African low-latitude region using actual TEC measurements by means of regional GPS receivers and data from the GIMs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
