Abstract
This paper focuses on the validation of the latest version of the International Reference Ionosphere (IRI-2016) model in predicting the vertical total electron content (VTEC) variation over Ethiopian ionospheric region during a high solar activity (2012-2016) phase. The diurnal, monthly and seasonal VTEC variations were analyzed from dual-frequency global positioning system (GPS) and IRI-2016 model at the Debark station. The diurnal, monthly and seasonal maximum TEC values measured between around 9:00 and 18:00 UT (12:00 and 21:00 LT) hours and the minimum TEC values measured before 9:00 (12:00 LT) and after 18:00 UT (21:00 LT). The overall results show that IRI-2016 model generally overestimates the diurnal, monthly and seasonal mean VTEC values during the high solar activity (2012-2016) phase. The model prediction generally follows that the monthly and seasonal variations of the measured VTEC values in equinoctial months are higher than solstice months. The monthly mean and seasonal mean values of IRI-TEC and GPS-TEC mostly correlates before early morning and after evening hours and also slightly IRI-TEC underestimates starting from morning hours up to evening hours. The magnetic storm effects on GPS-TEC are associated with fluctuations. However, the IRI-TEC values show smooth pattern during both in storm on and off options. Consequently, the IRI-2016 model does not correctly respond to the effects of the resulting storm disturbance.
Highlights
The large natural blanket of plasma in the atmosphere, which envelopes the Earth from an altitude of approximately 50 km to several thousands of kilometers is called the ionosphere
Diurnal variation of TEC is measured with different amount of total electron content between day, night and hourly TEC variation in 24 hours of a day
I have plotted about 57 diurnal variation of vertical total electron content (VTEC) and validation of International Reference Ionosphere model (IRI)-2016 model plots in between March 2012 to December 2016 and those plots are grouped in to three fits, which are best fit, intermediate fit and worst fit based on the performance of the IRI-2016 model estimates to detect TEC variation
Summary
The large natural blanket of plasma in the atmosphere, which envelopes the Earth from an altitude of approximately 50 km to several thousands of kilometers is called the ionosphere. The free electrons and ions are produced via ionization of the neutral particles both by extreme ultraviolet radiation from the Sun and by collisions with energetic particles that penetrate the atmosphere (Newell 1980). The ionized particles in the ionosphere are produced during the daytime through absorption of solar extreme ultraviolet and x-ray radiation by the atmospheric species. As the ionizing radiation from the sun penetrates deeper and deeper into the Earth’s atmosphere, it encounters a larger and larger density of gas particles, producing more and more electrons per unit volume (Bittencourt 2004). The recombination of free electrons with positive ions is a reversion of the photoionization and the recombination process is the main driver to produce neutral atoms (Limberger et al 2015)
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