Reliability of TEC over equatorial's region due to the seasonal changes
2008
S. Suhaili | M. Abdullah | A. Joseph | D. A. A. Mat | N. Misran
Equatorial zone is a unique region in the universe especially due to the irregularity behaviour of the number of Total Electron Content (TEC). This is normally caused by the existence of the most well known phenomenon called the Equatorial Anomaly (EA) or Appleton Hartree anomaly mainly occur during daytime on high solar activity. Besides, TEC also varied due to seasonal variations, such as equinoxes and solstices even though this places do not experienced the changes of the season compared to other places located at mid latitudes resulted from the location and position of the Sun from the Equatorial. This paper discussed the comparison of TEC using theoretical model, the International Reference Ionosphere 2001 (IRI2001) and NeQuick Ionospheric Model over equatorial during equinoxes and solstices. Results are compared to the real data of IONosphere Map Exchange (IONEX) format develop from the Center for Orbit Determination (CODE) in Europe. Study was done at Riau, Indonesia, which is exactly on the geographical equator. Results show high TEC on summer than that on winter of equatorial at night due to lower electron concentration and ion temperatures and vice versa during daytime. TEC calculated from models underestimate and overestimate the IONEX data. Major concern is in term of less number of earth station located nearby Riau leads to the problems of prediction made since these models depend on past data records observed from satellites, radars and in situ instruments which has several limitations. Due to the seasonal changes places located at the equatorial zonal also experiencing different value of TEC during the occurrence of solstices and equinoxes.
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