Analysis of the Probable Signature of Mid-Latitude Electron Density Trough at the Ionospheric Critical Frequencies over Europe

In this study, probable signature of mid-latitude electron density trough at the ionospheric critical frequencies is investigated. For this purpose, hourly ionospheric critical frequency (foF2) data obtained from ionosonde stations for the year 1972 is used. These stations are situated at between 45o - 66oinvariant magnetic latitudes (Λ) of the Northern hemisphere. foF2 data is investigated in terms of local time (LT), seasons, Λ and geomagnetic activity (Kp) variations. The results show that the troughs occur at nighttime hours between dusk and dawn sector for all situations. The troughs at geomagnetic active (Kp>2+) conditions are more prominent and apparent than that at geomagnetic quiet (Kp≤2+) conditions. The troughs and their minimum positions tend to occur at lower Λ for all four seasons at geomagnetic active conditions. Also, the average of foF2 values in the minimum points of the troughs has lower values at geomagnetic active conditions. It is observed that the seasonal variations have important effects on the structure of 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

YÜKSEK ENLEM foF2 DEĞERLERİNDEKİ DEĞİŞİMLERİN JEOMANYETİK AKTİVİTEYE BAĞLILIĞI

Bu çalışmada, Aralık 1971-Eylül 1972 tarihleri arasında yüksek enlem bölgesi olarak tanımlanan 60o-90o değişmeyen manyetik enlem arasındaki 7 iyonsonda istasyonundan alınan saatlik foF2 verilerinin değişmeyen manyetik enleme göre değişimleri, farklı jeomanyetik aktivite durumları için incelenmiştir. Analizlerden elde edilen sonuçlara göre, gündüz saatlerindeki foF2 değerlerinin, gece saatlerindeki değerlerden büyük olduğu, ayrıca bu saatlerde foF2 değerlerinin değişmeyen manyetik enlem artışı ile 68o-72o değişmeyen manyetik enlemleri arasındaki artış dışında azaldığı tespit edilmiştir. Gece saatlerinde ise foF2 değerlerinin yaklaşık 66o-72o değişmeyen manyetik enlemleri arasında arttığı, bu enlemlerden daha büyük ve daha küçük enlemlerde ise foF2 değerlerinin azalarak çukura benzer bir yapı oluşturduğu gözlemlenmiştir. Ayrıca mevsimsel ve jeomanyetik aktivite değişimlerinin, foF2 değerlerinin enlemsel değişimleri üzerinde önemli bir etkiye sahip olduğu tespit edilmiştir. Jeomanyetik pasif durumdaki foF2 değerleri, jeomanyetik aktif durumdaki foF2 değerlerinden büyüktür. Özellikle jeomanyetik aktif durumdaki Aralık döneminde, polar cap ve polar oval bölgeleri daha belirgin ve bu bölgeler enlemsel olarak daha geniş bir yapıya sahiptir

The effect of geomagnetic activity changes on the ionospheric critical frequencies (foF2) at magnetic conjugate points

In 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

The effect of geomagnetic activity changes on the ionospheric critical frequencies (foF2) at magnetic conjugate points

In 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