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Ramazan ATICI

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I am thirty nine years old. I am studying at Mus Alparslan University in Turkey. My proffesion is ionospheric physics. I am investigating the effects on the ionosphere from below and above. Recently, i am reserching space weather effects on the ionosphere. I teach advanced plasma waves at the university in graduate courses.

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Papers by Ramazan ATICI

Forecasting Future Monthly Patient Volume using Deep Learning and Statistical Models

Wireless Personal Communications, Mar 10, 2023

The variety of diseases is increasing day by day, and the demand for hospitals, especially for em... more The variety of diseases is increasing day by day, and the demand for hospitals, especially for emergency and radiology units, is also increasing. As in other units, it is necessary to prepare the radiology unit for the future, to take into account the needs and to plan for the future. Due to the radiation emitted by the devices in the radiology unit, minimizing the time spent by the patients for the radiological image is of vital importance both for the unit staff and the patient. In order to solve the aforementioned problem, in this study, it is desired to estimate the monthly number of images in the radiology unit by using deep learning models and statistical-based models, and thus to be prepared for the future in a more planned way. For prediction processes, both deep learning models such as LSTM, MLP, NNAR and ELM, as well as statistical based prediction models such as ARIMA, SES, TBATS, HOLT and THETAF were used. In order to evaluate the performance of the models, the symmetric mean absolute percentage error (sMAPE) and mean absolute scaled error (MASE) metrics, which have been in demand recently, were preferred. The results showed that the LSTM model outperformed the deep learning group in estimating the monthly number of radiological case images, while the AUTO.ARIMA model performed better in the statistical-based group. It is believed that the findings obtained will speed up the procedures of the patients who come to the hospital and are referred to the radiology unit, and will facilitate the hospital managers in managing the patient flow more efficiently, increasing both the service quality and patient satisfaction, and making important contributions to the future planning of the hospital.

The effect of lightning-induced electromagnetic waves on the electron temperatures in the lower ionosphere

kuwait journal of science, Nov 17, 2016

In this study, the heating of the nighttime lower ionosphere due to electromagnetic radiation in ... more In this study, the heating of the nighttime lower ionosphere due to electromagnetic radiation in the very low frequency (VLF) band that are transmitted by cloud-to-ground (CG) lightning return strokes is investigated. For this purpose, temperature of electrons in lower ionosphere is calculated by using electron energy balance equation, which is obtained by using Maxwellian distribution. In the result of calculations, in 10 V/m of the electrical field for all modes of electromagnetic (EM) wave, it was observed that the electron temperatures increased by about 9000-11000 K at an altitude of about 85-90 km. With an increase in the electric field, it was observed that the altitude, where the maximum temperatures were reached, shifted higher. The Right-Handed mode of the EM wave, unlike other modes was not return based-state to an altitude of 95-100 km. To fully determine the effect of lightning induced electromagnetic waves on the lower ionosphere, considering the effects of polarized modes (Right and Left) can also provide more information.

Yıldırım kaynaklı elektromanyetik dalgaların alt iyonküreyi ısıtma ve iyonlaşma süreçleri / Heating and ionization processes to lower ionosphere by lightning induced electromagnetic waves

Prediction of the Ionospheric foF2 Parameter Using R Language Forecasthybrid Model Library Convenient Time Series Functions

Wireless Personal Communications, 2021

Two different approaches of two different time-series models were used to predict the critical fr... more Two different approaches of two different time-series models were used to predict the critical frequency (foF2) of the ionospheric F2 layer over Athens (38.0° N, 23.5° E), Greece. Experimental foF2 data were obtained for the Athens station between 2004 and 2018. For the foF2 prediction, the R language forecasthybrid model library time-series convenient functions were used. Root mean square error (RMSE), mean absolute percent error (MAPE) and mean absolute error (MAE) performance metrics were used to examine the performances of the models. According to these tests, the predictions made with the cross-validation error approach are somewhat better than the equal-weighted-prediction approach. Besides, the predictions of foF2 were compared with those of the IRI-2016 model. According to the RMSE, MAE and MAPE analysis, the values of IRI-2016 model were 1.17 MHz, 1.00 MHz and 29.67%, whereas those of EWP and cross-validation errormodel were 0.40, 0.28 and 5.60 and 0.40, 0.27 and 5.56, respectively. Therefore, it can be said that the predictions of these time-series approaches used for the first time for the prediction of ionospheric foF2 are better than those of the IRI-2016. As a result, time-series algorithms, which are now living in the golden age, offer new opportunities for the prediction of ionospheric parameters as in other fields.

Calculation of the Ionospheric Cross-Section with the Incoherent Scattering Radar and Its Comparison with the Predictions of the IRI Model

Wireless Personal Communications

The Variation of Ionospheric TEC During Solar Eclipse on March 20, 2015

DergiPark (Istanbul University), Nov 4, 2021

This study aims to investigate the variation of Total Electron Content (TEC) during the solar ecl... more This study aims to investigate the variation of Total Electron Content (TEC) during the solar eclipse on 20 March 2015. For this purpose, TEC values obtained from five different GPS receivers [(morp, onsa, mar6, mets, tro1)] are examined for determining the ionospheric variation during the time of solar eclipse using percentage deviation calculation from mean values. To determine the impact of the solar eclipse, the TEC changes during the geomagnetically quiet (March 30) and the disturbing (March 19) days, as the reference days, are also studied. As a result of the examination, a behavior similar to a sunset in TEC values is observed in all stations when the percentage deviation calculations are considered. It is concluded that there is a decrease in morp, mets, mar6, onsa, and tro1 stations due to the solar eclipse by 16.45%, 6.53%, 7.99%, 8.12%, and 7.22%, respectively. There is an increase in TEC values on both reference days. However, the percentage of increase in the disturbing day is higher than the quiet day. It can be stated that the decreases in the ionospheric TEC at these five stations with eclipse size greater than 80% are due to the eclipse.

The Effect of Different Modes of HF Radio Wave to the Electron Temperature in Vertical Propagation at Subionosphere

Physical sciences, 2011

The Relationship of QBO with the Difference of Measured and Calculated NMF2

41st COSPAR Scientific Assembly, Jul 1, 2016

İyonkürenin E Bölgesi İçin NeQuick Modeli ile QBO Arasındaki İlişkinin İncelenmesi

Karaelmas Fen ve Mühendislik Dergisi, 2017

Investigation of TEC Variations over Mid-Latitude during Quit and Disturbed Days of March 2015

Investigation of Relationship between QBO and Ionospheric Neutral Temperature

Comparison with IRI-PLUS and IRI-2012-TEC values of GPS-TEC values

The Effect of QBO on the Total Mass Density

The relationship between TEC and Earth’s magnetic field during quiet and disturbed days over Istanbul, Turkey

Advances in Space Research, 2020

Abstract In this study, the impact of Earth’s magnetic field on total electron content (TEC) was ... more Abstract In this study, the impact of Earth’s magnetic field on total electron content (TEC) was studied by using statistical multiple linear regression model and co-integration method. TEC values were measured over the Turkey-Istanbul (ista) station using date of global positioning system (GPS), and the magnetic field components of the Earth were measured from Bogazici University, Kandilli Observatory and Earthquake Research Institute, Geomagnetic observatory Istanbul (ISK) station. This examination has been carried out during the dates of March 14-19, 2015 covering the dates of March 17-18, 2015 known in the literature as St. Patrick's Day geomagnetic storm. The three days before the storm (March 14-16) were named as quiet days, whereas the other days (March 17-19) were named as disturbed days after which the two periods were examined separately. It was observed as a result of the examination that the x-component (south-north direction) of the magnetic field had a negative impact on TEC on quiet days, whereas the impact was positive on disturbed days. However, the y-component (east-west direction) of the magnetic field had an inverse relationship of the x-component on the quiet and disturbed days. In addition, it was deduced that the impact coefficient of the x and y-component of the magnetic field was higher on disturbed days in comparison with those on quiet days. The correlation coefficient between the TEC and the components of the Earth’s magnetic field was 0.11 on quiet days and 0.95 on disturbed days. Therefore, it can be stated that the relationship of the TEC values with the geomagnetic field are higher on disturbed days.

Lower ionospheric electron density changes following lightning discharges

Acta Geophysica, 2018

The effect of lightning-induced electromagnetic (EM) waves on electron density (N e) of the lower... more The effect of lightning-induced electromagnetic (EM) waves on electron density (N e) of the lower ionosphere is calculated by using the four-component Glukhov-Pasko-Inan (GPI) model which is modified by including two-body attachment reactions and associative detachment with negative ions of active species (namely, O and N atoms). As a result of the calculations, it is seen that three-body attachment reactions take place at about 50-73 km altitudes, associative detachment takes place at approximately 73-85 km altitudes and two-body attachment reactions take place at approximately 85-95 km altitudes on the electron density. While the effect on electron density of electric field of lightning-induced EM wave is weak at altitudes where associative detachment is effective, it is strong at altitudes where two-body attachment reactions are effective. Also, it is shown that the electron density increases up to approximately 5.5 times when compared with the background density values due to electrons occurring as a result of associative detachment with negative ions of active species.

The possible effect of stratospheric quasi-biennial oscillation on the critical frequency of the ionospheric F2-layer

Pramana, 2018

In this study, the coupling between the stratospheric quasi-biennial oscillation (QBO) and the cr... more In this study, the coupling between the stratospheric quasi-biennial oscillation (QBO) and the critical frequency of the ionospheric F2-layer (foF2) was analysed statistically. The multiple regression model was used as a statistical tool. The model was developed by adding the sunspot number (SSN), which affects the foF2 (measured for Madras, Kodaikanal, Bogota, Manila and Tahiti) in the ionosphere at a significant level. Four different 'Dummy' sets of data were used in the model in order to observe the effect of the direction (east-west) and the magnitude (for both directions, between 0 and 15 m/s and between 0 and 16 m/s and the largest value) of QBO. It was observed that the variations of foF2 in the range of 60-78% in the model could be explained by SSN and SSN 2. The change of 2-13% that occurred in foF2 could be explained by the whole set of QBO. It was also observed that the effect of the direction and magnitude of QBO on foF2 differed between the stations.

The assessment in terms of QBO of NeQuick 2 model

The Egyptian Journal of Remote Sensing and Space Science, 2018

The NeQuick 2 model which is a model calculated to ionospheric parameter was evaluated in terms o... more The NeQuick 2 model which is a model calculated to ionospheric parameter was evaluated in terms of the stratospheric QBO. The relationship with QBO of the difference (DNmF1) was investigated by the multiple regression analysis model. DNmF1 defined as the difference (DNmF1 = NmF1 measured À NmF1 NeQuick 2) between the measured value from ionosonde and calculated value through the NeQuick 2 model of maximum electron density of the F1 region (NmF1). This investigation showed that the relationship at solar maximum case is stronger than the relationship at solar minimum case both in Darwin and in Learmonth stations. In solar minimum case, there are negative correlations between QBO and DNmF1 at both stations. In Darwin station, 67% of DNmF1 changes in case of solar maximum, 35% of DNmF1 changes in case of solar minimum can arise from the QBO. In Learmonth station, 51% of DNmF1 changes in case of solar maximum, 30% of DNmF1 changes in case of solar minimum can arise from the QBO. The results showed that the addition of QBO to the NeQuick 2 model would allow making calculations closing to actual data especially in the equator region of this model.

The Relationship of Stratospheric QBO with the Difference of Measured and Calculated NmF2

Acta Geophysica, 2016

The relationship between stratospheric QBO and the difference (ΔNmF2) between NmF2 calculated wit... more The relationship between stratospheric QBO and the difference (ΔNmF2) between NmF2 calculated with IRI-2012 and measured from ionosondes at the Singapore and Ascension stations in the equatorial region was statistically investigated. As statistical analysis, the regression analysis was used on variables. As a result, the relationship between QBO and ΔNmF2 was higher for 24:00 LT (local time) than 12:00 LT. This relationship is positive in the solar maximum epoch for both stations. In the solar minimum epoch, it is negative at 24:00 LT for Ascension and at 12:00 LT for Singapore. Furthermore, it was seen that the relationship of the ΔNmF2 with both the easterly and westerly QBO was negative for all solar epochs and every LT, at Ascension station. This relationship was only positive for solar maximum epoch and 12:00 LT, at Singapore station.

The Effect of QBO on foE

Advances in Space Research, 2017

Abstract In the present work, the relationship with QBO of difference (ΔfoE = foE mea − foE IRI ... more Abstract In the present work, the relationship with QBO of difference (ΔfoE = foE mea − foE IRI ) between critical frequency (foE) values of ionospheric E-region, measured at Darwin and Casos Island stations and calculated by IRI-2012 ionospheric model, is statistically investigated. A multiple regression model is used as statistical tool. The “Dummy” variables (“DummyWest” and “DummyEast” represent westerly QBO values and easterly QBO values, respectively) are added to model in order to see the effect of westerly and easterly QBO. In the result of calculations, it is observed that the changes in ΔfoE about 50–52% can be explained by QBO at both stations. The relationship between QBO and ΔfoE is negative at both stations. The change of 1 ms −1 in whole set of QBO leads to a decrease of 0.008 MHz at Casos Island station and 0.017 MHz at Darwin station in ΔfoE. Directions of QBO have an effect on ΔfoE at the Darwin station, but they’ve not any effect on ΔfoE at Casos Island station. It is thought that the difference values in the foE are due to not to be included in the IRI-model of all parameters affecting the critical frequency value. Thus, QBO which is not included to IRI-model can have an effect on foE and more accurate results can be obtained by IRI model if the QBO is included in this model calculations.

The Effect on Sporadic-E of Quasi-Biennial Oscillation

Journal of Physical Science and Application, 2016

In this study, the relationship between the QBO (quasi-biennial oscillation), which is seen at th... more In this study, the relationship between the QBO (quasi-biennial oscillation), which is seen at the equatorial stratosphere, and critical frequency of layer (Es) sporadically observed at the ionospheric E region was analyzed by using multiple regression model. For this analysis, Es layer critical frequency (foEs) obtained from four different stations at equatorial region and QBO measured at 10 hPa altitude values were used. The positive relationship between foEs and QBO was observed at all stations. An increase of 1 m/s at QBO leads to an increase of 0.01 Mhz, 0.02 Mhz, 0.02 Mhz and 0.01 Mhz (Jicamarca, Ascension, Manila and Kwajalein) on foEs, respectively. Expect for Manila station, westerly phase of QBO has greater effect on foEs compared to easterly phase of QBO at all other stations. It is seen that the changes occurred on foEs can be explained by the QBO at rates 47%, 46%, 32% and 44% for Jicamarca, Ascension, Manila and Kwajalein stations, respectively.

Forecasting Future Monthly Patient Volume using Deep Learning and Statistical Models

Wireless Personal Communications, Mar 10, 2023

The variety of diseases is increasing day by day, and the demand for hospitals, especially for em... more The variety of diseases is increasing day by day, and the demand for hospitals, especially for emergency and radiology units, is also increasing. As in other units, it is necessary to prepare the radiology unit for the future, to take into account the needs and to plan for the future. Due to the radiation emitted by the devices in the radiology unit, minimizing the time spent by the patients for the radiological image is of vital importance both for the unit staff and the patient. In order to solve the aforementioned problem, in this study, it is desired to estimate the monthly number of images in the radiology unit by using deep learning models and statistical-based models, and thus to be prepared for the future in a more planned way. For prediction processes, both deep learning models such as LSTM, MLP, NNAR and ELM, as well as statistical based prediction models such as ARIMA, SES, TBATS, HOLT and THETAF were used. In order to evaluate the performance of the models, the symmetric mean absolute percentage error (sMAPE) and mean absolute scaled error (MASE) metrics, which have been in demand recently, were preferred. The results showed that the LSTM model outperformed the deep learning group in estimating the monthly number of radiological case images, while the AUTO.ARIMA model performed better in the statistical-based group. It is believed that the findings obtained will speed up the procedures of the patients who come to the hospital and are referred to the radiology unit, and will facilitate the hospital managers in managing the patient flow more efficiently, increasing both the service quality and patient satisfaction, and making important contributions to the future planning of the hospital.

The effect of lightning-induced electromagnetic waves on the electron temperatures in the lower ionosphere

kuwait journal of science, Nov 17, 2016

In this study, the heating of the nighttime lower ionosphere due to electromagnetic radiation in ... more In this study, the heating of the nighttime lower ionosphere due to electromagnetic radiation in the very low frequency (VLF) band that are transmitted by cloud-to-ground (CG) lightning return strokes is investigated. For this purpose, temperature of electrons in lower ionosphere is calculated by using electron energy balance equation, which is obtained by using Maxwellian distribution. In the result of calculations, in 10 V/m of the electrical field for all modes of electromagnetic (EM) wave, it was observed that the electron temperatures increased by about 9000-11000 K at an altitude of about 85-90 km. With an increase in the electric field, it was observed that the altitude, where the maximum temperatures were reached, shifted higher. The Right-Handed mode of the EM wave, unlike other modes was not return based-state to an altitude of 95-100 km. To fully determine the effect of lightning induced electromagnetic waves on the lower ionosphere, considering the effects of polarized modes (Right and Left) can also provide more information.

Yıldırım kaynaklı elektromanyetik dalgaların alt iyonküreyi ısıtma ve iyonlaşma süreçleri / Heating and ionization processes to lower ionosphere by lightning induced electromagnetic waves

Prediction of the Ionospheric foF2 Parameter Using R Language Forecasthybrid Model Library Convenient Time Series Functions

Wireless Personal Communications, 2021

Two different approaches of two different time-series models were used to predict the critical fr... more Two different approaches of two different time-series models were used to predict the critical frequency (foF2) of the ionospheric F2 layer over Athens (38.0° N, 23.5° E), Greece. Experimental foF2 data were obtained for the Athens station between 2004 and 2018. For the foF2 prediction, the R language forecasthybrid model library time-series convenient functions were used. Root mean square error (RMSE), mean absolute percent error (MAPE) and mean absolute error (MAE) performance metrics were used to examine the performances of the models. According to these tests, the predictions made with the cross-validation error approach are somewhat better than the equal-weighted-prediction approach. Besides, the predictions of foF2 were compared with those of the IRI-2016 model. According to the RMSE, MAE and MAPE analysis, the values of IRI-2016 model were 1.17 MHz, 1.00 MHz and 29.67%, whereas those of EWP and cross-validation errormodel were 0.40, 0.28 and 5.60 and 0.40, 0.27 and 5.56, respectively. Therefore, it can be said that the predictions of these time-series approaches used for the first time for the prediction of ionospheric foF2 are better than those of the IRI-2016. As a result, time-series algorithms, which are now living in the golden age, offer new opportunities for the prediction of ionospheric parameters as in other fields.

Calculation of the Ionospheric Cross-Section with the Incoherent Scattering Radar and Its Comparison with the Predictions of the IRI Model

Wireless Personal Communications

The Variation of Ionospheric TEC During Solar Eclipse on March 20, 2015

DergiPark (Istanbul University), Nov 4, 2021

This study aims to investigate the variation of Total Electron Content (TEC) during the solar ecl... more This study aims to investigate the variation of Total Electron Content (TEC) during the solar eclipse on 20 March 2015. For this purpose, TEC values obtained from five different GPS receivers [(morp, onsa, mar6, mets, tro1)] are examined for determining the ionospheric variation during the time of solar eclipse using percentage deviation calculation from mean values. To determine the impact of the solar eclipse, the TEC changes during the geomagnetically quiet (March 30) and the disturbing (March 19) days, as the reference days, are also studied. As a result of the examination, a behavior similar to a sunset in TEC values is observed in all stations when the percentage deviation calculations are considered. It is concluded that there is a decrease in morp, mets, mar6, onsa, and tro1 stations due to the solar eclipse by 16.45%, 6.53%, 7.99%, 8.12%, and 7.22%, respectively. There is an increase in TEC values on both reference days. However, the percentage of increase in the disturbing day is higher than the quiet day. It can be stated that the decreases in the ionospheric TEC at these five stations with eclipse size greater than 80% are due to the eclipse.

The Effect of Different Modes of HF Radio Wave to the Electron Temperature in Vertical Propagation at Subionosphere

Physical sciences, 2011

The Relationship of QBO with the Difference of Measured and Calculated NMF2

41st COSPAR Scientific Assembly, Jul 1, 2016

İyonkürenin E Bölgesi İçin NeQuick Modeli ile QBO Arasındaki İlişkinin İncelenmesi

Karaelmas Fen ve Mühendislik Dergisi, 2017

Investigation of TEC Variations over Mid-Latitude during Quit and Disturbed Days of March 2015

Investigation of Relationship between QBO and Ionospheric Neutral Temperature

Comparison with IRI-PLUS and IRI-2012-TEC values of GPS-TEC values

The Effect of QBO on the Total Mass Density

The relationship between TEC and Earth’s magnetic field during quiet and disturbed days over Istanbul, Turkey

Advances in Space Research, 2020

Abstract In this study, the impact of Earth’s magnetic field on total electron content (TEC) was ... more Abstract In this study, the impact of Earth’s magnetic field on total electron content (TEC) was studied by using statistical multiple linear regression model and co-integration method. TEC values were measured over the Turkey-Istanbul (ista) station using date of global positioning system (GPS), and the magnetic field components of the Earth were measured from Bogazici University, Kandilli Observatory and Earthquake Research Institute, Geomagnetic observatory Istanbul (ISK) station. This examination has been carried out during the dates of March 14-19, 2015 covering the dates of March 17-18, 2015 known in the literature as St. Patrick's Day geomagnetic storm. The three days before the storm (March 14-16) were named as quiet days, whereas the other days (March 17-19) were named as disturbed days after which the two periods were examined separately. It was observed as a result of the examination that the x-component (south-north direction) of the magnetic field had a negative impact on TEC on quiet days, whereas the impact was positive on disturbed days. However, the y-component (east-west direction) of the magnetic field had an inverse relationship of the x-component on the quiet and disturbed days. In addition, it was deduced that the impact coefficient of the x and y-component of the magnetic field was higher on disturbed days in comparison with those on quiet days. The correlation coefficient between the TEC and the components of the Earth’s magnetic field was 0.11 on quiet days and 0.95 on disturbed days. Therefore, it can be stated that the relationship of the TEC values with the geomagnetic field are higher on disturbed days.

Lower ionospheric electron density changes following lightning discharges

Acta Geophysica, 2018

The effect of lightning-induced electromagnetic (EM) waves on electron density (N e) of the lower... more The effect of lightning-induced electromagnetic (EM) waves on electron density (N e) of the lower ionosphere is calculated by using the four-component Glukhov-Pasko-Inan (GPI) model which is modified by including two-body attachment reactions and associative detachment with negative ions of active species (namely, O and N atoms). As a result of the calculations, it is seen that three-body attachment reactions take place at about 50-73 km altitudes, associative detachment takes place at approximately 73-85 km altitudes and two-body attachment reactions take place at approximately 85-95 km altitudes on the electron density. While the effect on electron density of electric field of lightning-induced EM wave is weak at altitudes where associative detachment is effective, it is strong at altitudes where two-body attachment reactions are effective. Also, it is shown that the electron density increases up to approximately 5.5 times when compared with the background density values due to electrons occurring as a result of associative detachment with negative ions of active species.

The possible effect of stratospheric quasi-biennial oscillation on the critical frequency of the ionospheric F2-layer

Pramana, 2018

In this study, the coupling between the stratospheric quasi-biennial oscillation (QBO) and the cr... more In this study, the coupling between the stratospheric quasi-biennial oscillation (QBO) and the critical frequency of the ionospheric F2-layer (foF2) was analysed statistically. The multiple regression model was used as a statistical tool. The model was developed by adding the sunspot number (SSN), which affects the foF2 (measured for Madras, Kodaikanal, Bogota, Manila and Tahiti) in the ionosphere at a significant level. Four different 'Dummy' sets of data were used in the model in order to observe the effect of the direction (east-west) and the magnitude (for both directions, between 0 and 15 m/s and between 0 and 16 m/s and the largest value) of QBO. It was observed that the variations of foF2 in the range of 60-78% in the model could be explained by SSN and SSN 2. The change of 2-13% that occurred in foF2 could be explained by the whole set of QBO. It was also observed that the effect of the direction and magnitude of QBO on foF2 differed between the stations.

The assessment in terms of QBO of NeQuick 2 model

The Egyptian Journal of Remote Sensing and Space Science, 2018

The NeQuick 2 model which is a model calculated to ionospheric parameter was evaluated in terms o... more The NeQuick 2 model which is a model calculated to ionospheric parameter was evaluated in terms of the stratospheric QBO. The relationship with QBO of the difference (DNmF1) was investigated by the multiple regression analysis model. DNmF1 defined as the difference (DNmF1 = NmF1 measured À NmF1 NeQuick 2) between the measured value from ionosonde and calculated value through the NeQuick 2 model of maximum electron density of the F1 region (NmF1). This investigation showed that the relationship at solar maximum case is stronger than the relationship at solar minimum case both in Darwin and in Learmonth stations. In solar minimum case, there are negative correlations between QBO and DNmF1 at both stations. In Darwin station, 67% of DNmF1 changes in case of solar maximum, 35% of DNmF1 changes in case of solar minimum can arise from the QBO. In Learmonth station, 51% of DNmF1 changes in case of solar maximum, 30% of DNmF1 changes in case of solar minimum can arise from the QBO. The results showed that the addition of QBO to the NeQuick 2 model would allow making calculations closing to actual data especially in the equator region of this model.

The Relationship of Stratospheric QBO with the Difference of Measured and Calculated NmF2

Acta Geophysica, 2016

The relationship between stratospheric QBO and the difference (ΔNmF2) between NmF2 calculated wit... more The relationship between stratospheric QBO and the difference (ΔNmF2) between NmF2 calculated with IRI-2012 and measured from ionosondes at the Singapore and Ascension stations in the equatorial region was statistically investigated. As statistical analysis, the regression analysis was used on variables. As a result, the relationship between QBO and ΔNmF2 was higher for 24:00 LT (local time) than 12:00 LT. This relationship is positive in the solar maximum epoch for both stations. In the solar minimum epoch, it is negative at 24:00 LT for Ascension and at 12:00 LT for Singapore. Furthermore, it was seen that the relationship of the ΔNmF2 with both the easterly and westerly QBO was negative for all solar epochs and every LT, at Ascension station. This relationship was only positive for solar maximum epoch and 12:00 LT, at Singapore station.

The Effect of QBO on foE

Advances in Space Research, 2017

Abstract In the present work, the relationship with QBO of difference (ΔfoE = foE mea − foE IRI ... more Abstract In the present work, the relationship with QBO of difference (ΔfoE = foE mea − foE IRI ) between critical frequency (foE) values of ionospheric E-region, measured at Darwin and Casos Island stations and calculated by IRI-2012 ionospheric model, is statistically investigated. A multiple regression model is used as statistical tool. The “Dummy” variables (“DummyWest” and “DummyEast” represent westerly QBO values and easterly QBO values, respectively) are added to model in order to see the effect of westerly and easterly QBO. In the result of calculations, it is observed that the changes in ΔfoE about 50–52% can be explained by QBO at both stations. The relationship between QBO and ΔfoE is negative at both stations. The change of 1 ms −1 in whole set of QBO leads to a decrease of 0.008 MHz at Casos Island station and 0.017 MHz at Darwin station in ΔfoE. Directions of QBO have an effect on ΔfoE at the Darwin station, but they’ve not any effect on ΔfoE at Casos Island station. It is thought that the difference values in the foE are due to not to be included in the IRI-model of all parameters affecting the critical frequency value. Thus, QBO which is not included to IRI-model can have an effect on foE and more accurate results can be obtained by IRI model if the QBO is included in this model calculations.

The Effect on Sporadic-E of Quasi-Biennial Oscillation

Journal of Physical Science and Application, 2016

In this study, the relationship between the QBO (quasi-biennial oscillation), which is seen at th... more In this study, the relationship between the QBO (quasi-biennial oscillation), which is seen at the equatorial stratosphere, and critical frequency of layer (Es) sporadically observed at the ionospheric E region was analyzed by using multiple regression model. For this analysis, Es layer critical frequency (foEs) obtained from four different stations at equatorial region and QBO measured at 10 hPa altitude values were used. The positive relationship between foEs and QBO was observed at all stations. An increase of 1 m/s at QBO leads to an increase of 0.01 Mhz, 0.02 Mhz, 0.02 Mhz and 0.01 Mhz (Jicamarca, Ascension, Manila and Kwajalein) on foEs, respectively. Expect for Manila station, westerly phase of QBO has greater effect on foEs compared to easterly phase of QBO at all other stations. It is seen that the changes occurred on foEs can be explained by the QBO at rates 47%, 46%, 32% and 44% for Jicamarca, Ascension, Manila and Kwajalein stations, respectively.