The variability of foF2 in different phases of solar cycle 23 |
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| Authors: | Tamer Ataç Atila Özgüç R?za Pekta? |
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| Institution: | 1. Department of Physics, M L S University, Udaipur, India;2. New Resident Doctor Hostel, GB Pant Hospital, New Delhi 110002, India;1. Department of Industrial Physics, Landmark University, PMB 1001, Kwara State, Nigeria;2. Department of Physics, University of Ilorin, Ilorin, Nigeria;3. Lowell Digisonde International, LLC, 175 Cabot Street, Suite 200, Lowell, MA 01854, USA;4. Space Environment Research Center (SERC), Kyushu University, Fukuoka 812-8581, Japan;1. Università di Bologna “Alma Mater Studiorum”, Viale Berti Pichat 6/2, 40126 Bologna, Italy;2. Istituto Nazionale di Geo?sica e Vulcanologia, Via di Vigna Murata 605, 00143 Roma, Italy;1. Department of Physics, Landmark University, P.M.B. 1001, Omu Aran, Kwara State, Nigeria;2. Department of Physics, University of Ilorin, P.M.B. 1515, Ilorin, Kwara State, Nigeria;1. Pakistan Space and Upper Atmosphere Research Commission (SUPARCO), P.O. Box 8402, Karachi 75270, Pakistan;2. Asian Disaster Preparedness Center, SM Tower, 24th Floor, 979/69 Paholyothin Road, Samsen Nai Phayathai, Bangkok 10400, Thailand;3. China Research Institute of Radiowave Propagation (CRIRP), P.O. Box 6301, Qingdao 266107, China;4. Institute of Space Science and Technology, University of Karachi, Karachi 75270, Pakistan |
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| Abstract: | In this paper we examined the variations of the foF2 with solar activity for different local time and different seasons. Beside this we evaluated International Reference Ionosphere (IRI) models at different phases of solar cycle 23, different latitudes and different local time. We studied F2 layer critical frequency (foF2) of the ionosphere by using the flare index calculated by the Kandilli Observatory. For this purpose, we identified the months similar with high flare activity during the solar cycle 23. We chose 6 months which represented the different phases (ascending branch, maximum and descending branch) of the solar cycle. We also took into account the fact that these months were in different seasons. The hourly monthly means of observed foF2 data from four ionosonde stations for 6 months were calculated. On the other hand, the identical foF2 values of the same months were calculated for the year 1996, which is the minimum year of the previous solar activity cycle. We subtracted the foF2 values of 1996 from the values of the selected months of the last solar cycle to obtain the residuals, Δ(foF2). Then the magnitude of the residuals is compared through the cycle. We used IRI-2007 as well as IRI-2001 models to see the degree of deviation of the observed results from the predicted ones. We found that the predicted values of the ΔfoF2, which are calculated by the IRI-2007, fitted well with the observed Δ(foF2) and showed that the Δ(foF2) are dependent on the solar cycle variations in general. |
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