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Öğe An unusual spread-F-like event over Arecibo(Institute of Electrical and Electronics Engineers Inc., 2021) Bostan, Salih Mehmed; Urbina J.V.; Matthews J.D.; Breakall J.K.; DInsmore R.L.We describe an apparent mid-latitude spread-F-like event identified with the Arecibo Observatory (AO) incoherent scatter radar (ISR) but also observed using a newly introduced software-defined HF radar and via analysis of Global Positioning System-Total Electron Content (GPS-TEC) data. We show that this event was in fact nonlocal and appeared, as seen in delta-vTEC Keogram results to be propagating from west-to-east and back to the west crossing over AO twice. We suggest that this event, while indistinguishable from similar long ISR-observed events, has strong non-local properties. The combination of observations, from multiple instruments of this unique event helps tie its development and progression. The Penn State Ionospheric Radar Imager (PIRI), essentially a single frequency ionosonde, was deployed near AO (18.36° N, 66.75° W, 46.5° dip-angle, and fo = 4.42 MHz), Puerto Rico. The apparent PIRI-observed range spread of the event exceeds 400 km-a likely indication of spread-F viewed with an ionosonde. We also compare PIRI results with ISR and GPS-TEC results. ISR range-time intensity plots show rather a calm ionosphere, with exception of a major upwelling, that seems to include kilometer-scale layered structures, in the F-region. In contrast, the HF radar observations reveal that the ionosphere is disturbed by Perkins-like large scale instability structures. The data set is exceptional, consisting of simultaneous fixed frequency, wide-beam high frequency (HF) radar observations, ISR power intensity maps, and delta-vTEC measurements. These joint data sets characterized the nighttime ionosphere F-region and offer new insights into the ionospheric processes leading to what is observed by the very narrow-beam ISR.Öğe Cloverleaf Planar Antenna Designed for Synthetic Aperture Radar and Electronic Warfare Applications(Ieee, 2024) Bekdemir, Atakan Cagatay; Bostan, Salih MehmedThis paper is prepared for synthetic aperture radar applications in Electronic Warfare systems. The antenna is designed in 30.5x35.42x0.578 mm(3) size in the operating frequency range of 3.9-10.7 GHz for S, C and X bands. The antenna gain is in the range of 3.29 dBi-5.04 dBi and the antenna efficiency is in the range of 82.56%-98.07%. As a result of the study, the antenna far-field radiation pattern is a broadband pattern and the antenna axial ratio is circular polarisation.Öğe İyonosferik Uzaktan Algılama ve Radyo Astronomi Uygulamalarına Yönelik Geniş Bantlı Aktif Alıcı Anten Tasarımı(2023) Bostan, Salih Mehmed; Altıkardeşler, MertcanGünümüzde yüksek bant genişliği ve kompakt tasarım isterlerinden kaynaklı birçok haberleşme uygulaması UHF ve üstü bantlarını kullanmaktadır. Bu bantların yanı sıra UHF altı frekans bantlarının kendilerine has özellikleri bu bantlara olan ilginin devamlılığını sağlamaktadır. Bu bantlarda yapılan çalışmalara bakıldığında özellikle iyonosferik radar ve düşük frekans ( 100 MHz altı ) radyo astronomi uygulamaları gibi bilimsel çalışmaların ilgili bantları yoğun bir şekilde kullandığı gözlemlenmektedir. Söz konusu bantlarda frekansın düşmesi dalga boyunu artırmakta bu da çeşitli zorlukları beraberinde getirmektedir. Frekansın düşmesi ile antenlerin fiziksel boyutları artmakta ve yüksek bant genişliği isteyen uygulamalar için antenlerin mekanik yapısı çok fazla karmaşık bir hale gelebilmektedir. Bu duruma bir çözüm olarak literatürde trasistörlü ön-kuvvetlendiriciler ile tasarlanan aktif anten yapıları önerilmektedir. Pasif radyatör terminallerinde doğrudan bağlanan bir aktif devre ile anten boyutları önemli ölçüde düşürülebilmektedir. Bu çalışmada 1 ? 50 MHz arası iyonosferik radar ve düşük frekans radyo astronomi uygulamalarına yönelik bir aktif alıcı anten tasarımı gerçekleştirilmiştir.Öğe Multi-instrument study of a spread-F event at Arecibo linked to solar wind variations(Pergamon-Elsevier Science Ltd, 2023) Bostan, Salih Mehmed; Urbina, Julio, V; Mathews, John D.; Dinsmore, Ross L.; Robinson, Robert M.Using five diverse data sets, we demonstrate that apparently local ionospheric spread-F activity, observed with an HF radar and the Arecibo Observatory (AO) Incoherent Scatter Radars (ISR) under geomagnetically quiet conditions, is likely the local manifestation of a mesoscale or larger ionospheric response to relatively weak solar wind activity. The solar wind activity included a weak pressure pulse and Interplanetary Magnetic Field (IMF) realignment events. The mid-latitude spread-F activity was observed with a 4.42 MHz radar located near AO and the dual-beam 430 MHz AO ISRs. Additionally, the Coupling, Energetics and Dynamics of Atmospheric Regions (CEDAR) Madrigal Global Navigation Satellite System-Total Electron Content (GNSS-TEC), the NASA OMNI, and the SuperMAG datasets were used to establish the (mesoscale/global) wide-context of the local, deep-context radar results. While the ISR event appears to be classicallocal spread-F, often attributed to Perkins-like plasma instabilities, the HF radar reveals large ionospheric structures coincident with the ISR event. However, that the apparently AO-local event was part of a very dynamic mesoscale event that lasted for over ten hours, is shown via independent AO-sector and AO-conjugate sector keograms constructed using detrended vertical TEC (delta-vTEC) data. The keograms reveal a prominent F-region feature that appears to propagate from west-to-east and then back to the west passing over AO twice. The ISR manifestation of this mesoscale event is indistinguishable from decades of similar ISR results which were assumed to be strictly local. The strong non-local (mesoscale) properties revealed by the delta-vTEC keograms suggest a possible space weather influence. Study of the relevant NASA OMNI solar wind and superMAG magnetometer data points to modest solar wind features including IMF realignment that may have electrodynamically launched, with little time delay, the observed mesoscale ionospheric events. Given the apparent rapid ionospheric response to the solar wind features, we suggest that limited latitudinal scale, prompt penetration electric fields (PPEF), associated with highly-localized partial ring current activity, be considered in the system-of-systems context of our observations. In any case, the need to examine magnetospheric/ionospheric electrodynamics across a wide range of instruments and data sets is demonstrated.
