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Performance analysis of IRI 2016 model TEC predictions over Northern and Southern Hemispheric IGS stations during descending phase of solar cycle 24

Nibigira Jean de Dieu, Sivavaraprasad G., Ratnam D. Venkata

Acta Geophysica

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2021

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Vol. 69, no. 4

1509--1527

EN

Global Positioning System (GPS) is an efective tool for monitoring the Earth’s ionosphere. This paper concerns with temporal and spatial variations of ionospheric total electron content (TEC) at RAMO, Israel (geographic coordinates: 30.597o N, 34.76o E; geomagnetic coordinates: 27.17o N, 112.40o E), and ZAMB, Zambia (geographic coordinates: 15.42o S, 28.31o E; geomagnetic coordinates: 16.98o S, 98.67o E) for the descending phase of solar cycle-24. The VTEC estimated from GPS measurements and VTEC values modeled from the IRI-2016 model are obtained over both the GPS stations, i.e., RAMO station, in Northern Hemisphere (NH) and ZAMB station in Southern Hemisphere (SH). The diurnal, seasonal, annual, and solar cycle variations in TEC are investigated during 2016–2018. Also, a comparative study is performed between VTEC derived from GPS observations and International Reference Ionosphere-2016 (IRI-2016) model using the statistical analysis. It has been observed that the observed and modeled maximum VTEC decreases with the declining phase of solar cycle-24 over both the stations. The semiannual patterns are noticed in VTEC values of both the IRI-2016 model and GPS observations for all the years, i.e., 2016–2018. At RAMO station, seasonal analysis depicted a year-wise decrease in maximum TEC as follows March Equinox (Mar-Equ), September Equinox (Sep-Equ), December Solstice (Dec-Sol), and June Solstice (Jun Sol). It is observed from the monthly average estimations of the IRI-2016 model that it has relatively more overestimations of VTEC values over RAMO station in NH than over ZAMB in SH during 2016–2018. However, the IRI-2016 model has underestimated the GPS-VTEC values from June–September 2018 over NH, RAMO station. The root-mean-square error (RMSE) values of the IRI-2016 model delineate that the model has more RMSE during March Equinox than September Equinox, whereas these RMSEs are recorded high over NH (RAMO) than SH (ZAMB). At RAMO, the IRI-2016 model has shown high RMSE values during the June solstice compared to the December solstice. On the other hand, at ZAMB, the highest RMSE values are observed during the December solstice than June solstice. Ionolab-TEC and GIM-TEC also considered over both the stations for the analysis. The IRI-2016 model predictions are in good agreement with GPS-VTEC values over SH (ZAMB) compared to NH (RAMO).

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Wpływ aktywności słonecznej na propagację fal radiowych

Wilk-Jakubowski J.

Autobusy : technika, eksploatacja, systemy transportowe

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2016

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R. 17, nr 12

1454--1457

PL

Wszelkie procesy mające miejsce na powierzchni Słońca oraz w jego atmosferze mają wpływ na powstawanie zaburzeń promieniowania elektromagnetycznego, które dociera do Ziemi oraz fluktuacji wiatru słonecznego. W tym kontekście niezbędne wydaje się być wyjaśnienie tego zjawiska, tym bardziej, że w ostatnich latach notowano podwyższoną aktywność słoneczną. Co więcej, pojawiają się pierwsze doniesienia o istniejącym związku pomiędzy aktywnością słoneczną, a czasem życia ludzi. W niniejszym artykule przedstawiono część badań i analiz dotyczących wpływu aktywności słonecznej na propagację fal radiowych, ilustrujących związek pomiędzy zmianami cyklu słonecznego a tłumieniem fal radiowych, długoterminowy rozkład aktywności słonecznej oraz zmian temperatury, a także przykładowe okresy interferencji słonecznych wyznaczone z użyciem metod komputerowych.

EN

Paper discussed the impact of solar activity on the radio waves propagation on the basis of satellite signal. In this context the Author presents e.g. extraterrestrial natural noise sources, the influence of changes in the solar cycle on the radio wave propagation among selected frequency, the distribution of solar activity and the changes in temperature in 130 years. Moreover the Author presents the approximated periods of solar interferences for EUTELSAT Hot Bird 13A, 13B and 13C satellites.

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GPS Amplitude Scintillations over Kampala, Uganda, During 2010-2011

Akala A. O., Idolor R., D'Ujanga F. M., Doherty P. H.

Acta Geophysica

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2016

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Vol. 64, no. 5

1903--1915

EN

This study characterizes equatorial scintillations at L1/L2 GPS frequency over Kampala (0.30°N, 32.50°E, mag. lat. 9.26°S), Uganda, on different time scales during the minimum and ascending phases of solar cycle 24 (2010-2011). Of all the days investigated, 25 October 2011 recorded the highest occurrence of scintillation, and it was attributed to geomagnetic storm occurrence. We used the data of 25 October to generate plots of the elevation angle and S4 index against local time on a satellite-by-satellite basis, with a view to distinguishing satellites links whose signals were impaired by ionospheric irregularities from those impaired by multipath. Conclusively, GPS amplitude scintillations over Kampala occur predominantly during post sunset hours and decay around midnight. Equinoctial months recorded the highest occurrences of scintillations, while June solstice recorded the least. Scintillation occurrences also increase with solar and geomagnetic activity.