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Öğe A Comparison of IRI-2016 foF2 Predictions with the Observations at Different Latitudes During Geomagnetic Storms(Maik Nauka/Interperiodica/Springer, 2018) Timocin, E.; Unal, I.; Goker, U. D.This study investigates the impacts of geomagnetic storms on the performance of the International Reference Ionosphere 2016 (IRI-2016) foF2 predictions at different latitudes during geomagnetically disturbed periods in different seasons of the year 1989 which is around maximum solar activity. For this purpose, hourly foF2 data measured from the ionosonde stations Manila (14.7 degrees N, 121.1 degrees E), Rome (41.8 degrees N, 12.5 degrees E), Argentia NF (47.3 degrees N, 54.0 degrees W) and Uppsala (59.8 degrees N, 17.6 degrees E) that are located at low, middle and high latitudes, and hourly foF2 data calculated from the IRI-2016 for the same locations are used. In our study, a comparison between observational results and that of the IRI-2016 foF2 predictions is made. Planetary geomagnetic activity 3h-K-p and 3h-a(p) indices are used as geomagnetic activity indicators. In order to test the performance of the IRI-2016 for disturbed geomagnetic conditions, the percentile deviations and root mean square errors (RMSE) are calculated using the foF2 data from the IRI-2016 and the ionosonde stations. These analyzes are done for four seasons based on geomagnetic stormy days around equinoxes (March 21, September 23) and solstices (June 21, December 21). Therefore, it is found that during geomagnetically disturbed periods, the IRI-2016 foF2 predictions deviate considerably from the foF2 data taken from the ionosonde stations and this deviation differs according to the seasons and latitudes. The results show that the last version of the IRI model that includes the foF2 storm model is not sufficient to properly represent the real conditions of a disturbed ionosphere and there is still space for improving the IRI model for geomagnetically disturbed conditions.Öğe The effect of altitude and season on dielectrical relaxation mechanism of ionospheric plasma(Soc Italiana Fisica, 2009) Yesil, A.; Unal, I.In this paper, the effect of altitude and season on dielectrical relaxation mechanism of ionospheric plasma has been investigated. The real and imaginary parts of the dielectric constant with respect to altitude were seasonally calculated. The real and imaginary parts of the dielectric constant change with altitude and season, so the plasma frequency does. The imaginary part of the dielectric constant shows a relaxation peak and peak position shifts to lower altitudes. In the F region, the real part of the dielectric constant is very lower due to the excessive electron exchanges. This suggests that the determination of the dielectrical properties of the F-region is very important to explain the propagation of electromagnetic waves in the F region, because the propagation of electromagnetic waves in the F region is affected by the dielectrical properties of the ionosphere.Öğe IONOSPHERIC ABSORPTION OF HF RADIO WAVE IN VERTICAL PROPAGATION(Shiraz Univ, 2007) Unal, I.; Ozcan, O.; Canyilmaz, M.In this study, absorption of high frequency radio waves in the ionospheric plasma have been investigated. The wave equation was obtained in terms of ionospheric parameters. The numerical values of the absorption have been calculated for 4 MHz, 4.5 MHz and 5 MHz waves. The necessary parameters for calculation have been obtained using an International Reference ionosphere (IRI) Model. The altitudinal, diurnal, seasonal and the variations of absorption with frequency have been examined. The calculations show that the highest absorption Occurs in the D-region. The absorption is higher in Summer than in other seasons and is maximum at daylight. In addition, absorption decreases with the increase of frequency.Öğe A RESEARCH FOR BASIC ASTRONOMY KNOWLEDGE LEVEL OF SCIENCE TEACHERS(Scibulcom Ltd, 2015) Tascan, M.; Unal, I.Astronomy, which contains many science disciplines within itself, is used for acquiring information on the concept level and making people love science all over the world. In this study, the determination of science teachers knowledge in the basic astronomy subjects is aimed at. An astronomy knowledge test has been developed in order to determine the knowledge level of the teachers. The study was designed as descriptive model and mixed method that combines quantity and quality researches were used. According to the findings, at the end of the study, it has been seen that the teachers lack the basic astronomical subjects such as Solar System, Moon tilt of orbit, axial tilt of the Earth, Lunar and Solar eclipse, astronomy unit and light year as well as the subjects like concretion of an event in their minds, relation of cause and effect and three dimensional thinking. Also, in terms of final results, it turned out to be that the teachers interest in the astronomical subjects is so low and they know the book information but they are not successful at relating this information with each other and their cause and effects.
