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

Tulunay, Yurdanur
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 neural network technique - 2: an ionospheric example illustrating its application
Tulunay, Yurdanur; Tulunay, E; Senalp, ET (Elsevier BV, 2004-01-01)
An example of modeling of Near Earth Space Processes by empoying the Neural Network Approach [Tulunay et al., Adv. Space Res., this current issue, 2003] is considered. The temporal and spatial forecasting of ionospheric critical frequency f(o)F2 values up to 24 h in advance by using the METUNN model is briefly covered. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.
On the wake pattern of symmetric airfoils for different incidence angles at Re=1000
Kurtuluş, Dilek Funda (SAGE Publications, 2016-06-01)
In the current study, numerical simulations are performed in order to investigate effects of incidence angle and airfoil thickness on alternating vortex pattern of symmetric airfoils at Re = 1000. This alternating vortex pattern is found to be significantly varying in shape as the incidence angle increases. The results are obtained with 1 degrees increment from 0 degrees to 41 degrees and then with 10 degrees increment from 40 degrees until 180 degrees. The instantaneous and mean vortex patterns are investi...
Non-parametric regional VTEC modeling with Multivariate Adaptive Regression B-Splines
Durmaz, Murat; Karslıoğlu, Mahmut Onur (Elsevier BV, 2011-11-01)
In this work Multivariate Adaptive Regression B-Splines (BMARS) is applied to regional spatio-temporal mapping of the Vertical Total Electron Content (VTEC) using ground based Global Positioning System (GPS) observations. BMARS is a non-parametric regression technique that utilizes compactly supported tensor product B-splines as basis functions, which are automatically obtained from the observations. The algorithm uses a scale-by-scale model building strategy that searches for B-splines at each scale fittin...
Effect of Thickness-to-Chord Ratio on Flow Structure of a Low Swept Delta Wing
Gulsacan, Burak; Sencan, Gizem; Yavuz, Mehmet Metin (American Institute of Aeronautics and Astronautics (AIAA), 2018-12-01)
The effect of thickness-to-chord (t/C) ratio on flow structure of a delta wing with sweep angle of 35 deg is characterized in a low-speed wind tunnel using laser-illuminated smoke visualization, particle image velocimetry, and surface pressure measurements. Four different t/C ratios varying from 4.75 to 19% are tested at angles of attack, 4, 6, 8, and 10 deg, for Reynolds numbers Re =1 x 10(4) and 3.5 x 10(4). The results indicate that the effect of thicknessto-chord ratio on flow structure is quite substan...
On period and burst histories of AXPs and SGRs and the possible evolution of these objects on the P-P diagram
Guseinov, OH; Yazgan, EFE; Ankay, A; Tagieva, S (World Scientific Pub Co Pte Lt, 2003-01-01)
In this paper, timing data for anomalous X-ray pulsars and soft gamma repeaters are compiled. Timing properties of these objects are investigated. The effect of bursts of soft gamma repeaters on their period history is investigated. The P-P diagram for pulsars, X-ray binaries, anomalous X-ray pulsars, soft gamma repeaters and dim radio quiet neutron stars is constructed. The possible evolutionary tracks for anomalous X-ray pulsars, soft gamma repeaters and dim radio quiet neutron stars are examined.
Citation Formats
E. TİMOÇİN, İ. ÜNAL, Y. Tulunay, and Ü. D. GÖKER, “The effect of geomagnetic activity changes on the ionospheric critical frequencies (foF2) at magnetic conjugate points,” ADVANCES IN SPACE RESEARCH, pp. 821–828, 2018, Accessed: 00, 2020. [Online]. Available: