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Mapping the East African Ionosphere Using Ground-based GPS TEC Measurements
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 Title & Authors
Mapping the East African Ionosphere Using Ground-based GPS TEC Measurements
Mengist, Chalachew Kindie; Kim, Yong Ha; Yeshita, Baylie Damtie; Workayehu, Abyiot Bires;
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The East African ionosphere (3°S-18°N, 32°E-50°E) was mapped using Total Electron Content (TEC) measurements from ground-based GPS receivers situated at Asmara, Mekelle, Bahir Dar, Robe, Arbaminch, and Nairobi. Assuming a thin shell ionosphere at 350 km altitude, we project the Ionospheric Pierce Point (IPP) of a slant TEC measurement with an elevation angle of >10° to its corresponding location on the map. We then infer the estimated values at any point of interest from the vertical TEC values at the projected locations by means of interpolation. The total number of projected IPPs is in the range of 24-66 at any one time. Since the distribution of the projected IPPs is irregularly spaced, we have used an inverse distance weighted interpolation method to obtain a spatial grid resolution of 1°×1° latitude and longitude, respectively. The TEC maps were generated for the year 2008, with a 2 hr temporal resolution. We note that TEC varies diurnally, with a peak in the late afternoon (at 1700 LT), due to the equatorial ionospheric anomaly. We have observed higher TEC values at low latitudes in both hemispheres compared to the magnetic equatorial region, capturing the ionospheric distribution of the equatorial anomaly. We have also confirmed the equatorial seasonal variation in the ionosphere, characterized by minimum TEC values during the solstices and maximum values during the equinoxes. We evaluate the reliability of the map, demonstrating a mean error (difference between the measured and interpolated values) range of 0.04-0.2 TECU (Total Electron Content Unit). As more measured TEC values become available in this region, the TEC map will be more reliable, thereby allowing us to study in detail the equatorial ionosphere of the African sector, where ionospheric measurements are currently very few.
East African ionosphere;total electron content;GPS;inverse distance weighted interpolation;equatorial anomaly;
 Cited by
On the Variability of the Ionospheric F2-Layer During the Quietest Days in December 2009,;;

Journal of Astronomy and Space Sciences, 2016. vol.33. 4, pp.273-278 crossref(new window)
On the Variability of the Ionospheric F2-Layer During the Quietest Days in December 2009, Journal of Astronomy and Space Sciences, 2016, 33, 4, 273  crossref(new windwow)
Appleton EV, The anomalous equatorial belt in the F2-layer, J. Atmos. Terr. Phys. 5, 348-351 (1954). crossref(new window)

Ciraolo L, Azpilicueta F, Brunini C, Meza A, Radicella SM, Calibration errors on experimental slant total electron content (TEC) determined with GPS, J. Geod. 81, 111-120 (2007). crossref(new window)

Durmaz M, Non-parametric and semi-parametric regional modeling of the ionospheric vertical total electron content using ground-based gps observations, PhD Dissertation, Middle East Technical University (2013).

Feltens J, Jakowski N, The International GPS Service (IGS) Ionosphere Working Group Activity, SCAR Report No. 21 (2002).

Grejner-Brzezinska DA, Wielgosz P, Kashani I, Smith DA, Spencer PSJ, et al., An analysis of the effects of different network-based ionosphere stimation models on rover positioning accuracy, J. Glob. Position. Syst. 3, 115-131 (2004). crossref(new window)

Grejner-Brzezinska DA, Wielgosz P, Kashani I, Smith DA, Robertson DS, et al., The Impact of Severe Ionospheric Conditions on the Accuracy of Kinematic Position Estimation: Performance Analysis of Various Ionosphere Modeling Techniques, Navigation 53, 203-217 (2006). crossref(new window)

Hemtindez-Pajares M, Juan JM, Sanz J, Colombo OL, Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN,14-17 September 1999.

Hofmann-Wellenhof B, Lichtenegger H, Collins J, Global Positioning System: Theory and Practice (Springer-Verlag, Wien, 2001).

Kintner PM, Ledvina BM, The ionosphere, radio navigation, and global navigation satellite systems, Adv. Space Res. 35, 788-811 (2005). crossref(new window)

Klobuchar JA, Design and characteristics of the GPS ionospheric time delay algorithm for single frequency users, in 1986 Position Location and Navigation Symposium, Las Vegas, NV, 4-7 November 1986.

Komjathy A, Global Ionospheric Total Electron Content Mapping Using the Global Positioning System, PhD Dissertation, University of New Brunswick (1997).

Mannucci AJ, Wilson BD, Yuan DN, Ho CH, Lindqwister UJ, et al., A Global mapping technique for GPS-derived ionospheric total electron content measurements, Radio Sci. 33, 565-582 (1998). crossref(new window)

Maruyama T, Ma G, Nakamura M, Signature of TEC storm on 6 November 2001 derived from dense GPS receiver network and ionosonde chain over Japan, J. Geophys. Res. 109, A10302 (2004). crossref(new window)

Pi X, Wang C, Hajj GA, Rosen G, Wilson BD, et al., Estimation of E×B drift using a global assimilative ionospheric model: An observation system simulation experiment, J. Geophys. Res. 108, 1075 (2003), crossref(new window)

Tsai HF, Liu JY, Tsai WH, Liu CH, Tseng CL, et al., Seasonal variations of the ionospheric total electron content in Asian equatorial anomaly regions. J. Geophys. Res. 106, 30363-30369 (2001). crossref(new window)

Yu T, Wan WX, Liu LB, Tang W, Luan XL, et al., Using IGS data to analysis the global TEC annual and semiannual variation, Chin. J. Geophys. 49, 943-949 (2006).