Yazar "Timocin, Erdinc" seçeneğine göre listele
Listeleniyor 1 - 5 / 5
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Analysis of the Probable Signature of Mid-Latitude Electron Density Trough at the Ionospheric Critical Frequencies over Europe(Ist Nazionale Di Geofisica E Vulcanologia, 2017) Timocin, Erdinc; Unal, IbrahimIn this study, probable signature of the mid-latitude electron density trough at the ionospheric critical frequencies (foF2) is investigated. For this purpose, hourly ionospheric critical frequencies data obtained from ionosonde stations for the year 1972 are used. These stations are situated between 45 degrees-65 degrees invariant magnetic latitudes (Lambda) of the Northern hemisphere. The foF2 data are examined depending on local time (LT), seasons,. and geomagnetic activity (K-p) variation. The results show that the foF2 troughs occur in the nighttime hours between dusk and dawn sector for all situations. The troughs under geomagnetic active (K-p > 2(+)) conditions are more prominent and apparent than that under geomagnetic quiet (K-p <= 2(+)) conditions. Under geomagnetic active conditions, the troughs and their minimum positions tend to appear at lower. for four seasons. Also, the average foF2 values of the trough minimum under geomagnetic active conditions have lower values than that under geomagnetic quiet conditions. It is observed that the seasonal variations have important effects on the structure of the foF2 trough, especially for December Solstice. The results of this study will contribute a better description and prediction of the mid-latitude electron density trough features for the ionospheric F2 peak heights and better understanding the role of the mid-latitude electron density trough on the ionospheric variability.Öğe The effect of geomagnetic activity changes on the ionospheric critical frequencies (foF2) at magnetic conjugate points(Elsevier Sci Ltd, 2018) Timocin, Erdinc; Unal, Ibrahim; Tulunay, Yurdanur; Goker, Umit DenizIn this work, we investigate the possible effects of geomagnetic activity on the ionospheric critical frequencies (foF2) in geomagnetic conjugate points. For this purpose, hourly foF2 data measured for the year 1976 from the ionosonde stations Akita, St. John's and Resolute Bay in the Northern hemisphere and their corresponding magnetic conjugate ionosonde stations Brisbane, Halley Bay and Scott Base in the Southern hemisphere are examined. Planetary geomagnetic activity 3h-K-p indices are used as a geomagnetic activity indicator. foF2 data in the magnetic conjugate points (MCP) are investigated by using a superposed epoch analysis method. This analysis is done depending on the response of foF2 to geomagnetic activity variations in MCP based on geomagnetic stormy days around equinoxes (March 21, September 23) and solstices (June 21, December 21), and the results obtained from these MCP are compared. From these results, it is found that foF2 values in magnetic conjugate pairs give similar reactions to geomagnetic activity variations simultaneously, although this relationship differs according to the seasons and magnetic latitudes of the stations. (C) 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.Öğe The effect of the geomagnetic activity to the hourly variations of ionospheric foF2 values at low latitudes(Springer Heidelberg, 2014) Timocin, Erdinc; Yesil, Ali; Unal, IbrahimIn this study, the relationship between the hourly changes of the ionospheric critic frequency values of F2 layers in low latitudes and geomagnetic activity is examined by using statistical methods. The ionospheric critical frequency data has been taken from the Manila (121.1A degrees A E, 14.7A degrees A N) ionosonde station. In order to investigate the effect of sun activity on ionospheric critical frequency, the data of 1981 when the sun was active and of 1985 when the sun was less active has been used. According to the Granger causality test results, on 5 % significance level, a causality relationship from disturbance storm time (Dst) index values to ionospheric critical frequency values direction has been observed. However, a causality relationship from ionospheric critical frequency values to Dst values has not been observed. From the results of cause-and-effect analysis, it is evaluated that the effect of a shockwave occurring in geomagnetic activity on ionospheric critical frequency continues along 72 h, that is, geomagnetic activity has a long-term effect on ionospheric critical frequency. The response of ionospheric critical frequency to geomagnetic activity substantially depends on seasons. This response is more observed especially in equinox period when the sun is active and in winter months. The increase in geomagnetic activity causes ionospheric critical frequency to decrease in night hours and increase in day hours. The same relationship has not been observed exactly, though observed very little in winter months, for 1985 when the sun was less active.Öğe The Effect of the Midlatitude Electron Density Trough on the Ionospheric Conductivities(Springer International Publishing Ag, 2019) Timocin, Erdinc; Unal, Ibrahim; Yesil, AliIn this study, we have investigated the effect of midlatitude electron density trough on ionospheric conductivities for different altitudes. For this purpose, parallel conductivity (sigma (0)), Pedersen conductivity (sigma (1)) and Hall conductivity (sigma (2)) data were calculated by using the International Reference Ionosphere (IRI) model for seven different geographic coordinates in the midlatitude region of the northern hemisphere during the June and December solstices of 1972. Planetary geomagnetic activity index () data are used as a geomagnetic activity indicator. These conductivity values computed for each position were classified according to geomagnetic active () and geomagnetic quiet () conditions; and these values were examined according to invariant magnetic latitudes (I >) for different heights, seasonal, geomagnetic activity and local times. From the analysis results, it is found that the midlatitude electron density trough does not have any effects on sigma (0) for all situations, but the trough is influential on sigma (1) and sigma (2) during night hours of the December solstices. In addition, it was observed that the trough increased its effect on sigma (1) and sigma (2) with the increasing geomagnetic activity level and altitude for December solstices.Öğe The Responses of Ionospheric Conductivities on the Mid-Latitudes to Changes in the BZ Component of Interplanetary Magnetic Field(Springer, 2020) Timocin, Erdinc; Yesil, Ali; Unal, IbrahimIn this study, we investigate the response of the ionospheric conductivities on the middle latitudes to the southward and northward turnings of the B-Z component of the interplanetary magnetic field (IMF). For this purpose, parallel conductivity (sigma(0)), Pedersen conductivity (sigma(1)), Hall conductivity (sigma(2)) data calculated for Rome (41.8 degrees N, 12.5 degrees E); Juliusruh (54.6 degrees N, 13.4 degrees E); Uppsala (59.8 degrees N, 17.6 degrees E); Lycksele (64.7 degrees N, 18.8 degrees E) during the 22nd solar cycle are examined. The superposed epoch analysis method is used to investigate the response of the conductivities to the southward and northward turnings of the B-Z component. From the analysis results it is observed that the turnings in the B-Z component of the IMF have significant effect on all conductivities. At the event moment (zero time), the southward turnings of the B-Z component increases all conductivities while the northward turnings of the B-Z component decreases all conductivities. The effect on the conductivities of the changes in the B-Z component occurs before about 18 h from the event moment, and this effect disappears after about 24 h from the event moment. Furthermore, all of ionospheric conductivities shows or does less reaction to changes in the B-Z component as latitude increase.
