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Tsugawa, T.
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Tsugawa, T.
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- PublicationOpen AccessLow-latitude equinoctial spread-F occurrence at different longitude sectors under low solar activity(2013-02-05)
; ; ; ; ; ; ; ; ; ; ; ; ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Abadi, P.; Division of Ionosphere and Telecommunication, Space Science Center, Indonesian National Institute of Aeronautics and Space (LAPAN), Indonesia ;A.J. de Abreu, A. J.; Universidade do Vale do Paraíba, São José dos Campos, Brazil ;de Jesus, R.; Universidade do Vale do Paraíba, São José dos Campos, Brazil ;Fagundes, P. R.; Universidade do Vale do Paraíba, São José dos Campos, Brazil ;Supnithi, P.; Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand ;Rungraengwajiake, S.; Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand ;Nagatsuma, T.; Space Weather and Environment Informatics Laboratory, National Institute of Information and Communications Technology, Tokyo 184-8795, Japan ;Tsugawa, T.; Space Weather and Environment Informatics Laboratory, National Institute of Information and Communications Technology, Tokyo 184-8795, Japan ;Cabrera, M. A.; Laboratorio de Telecomunicaciones, DEEC, FACET, Universidad Nacional de Tucumán, Tucumán, Argentina ;Ezquer, R. G.; Laboratorio de Ionósfera, Departamento de Física, FACET, Universidad Nacional de Tucumán, Tucumán, Argentina; ; ; ; ; ;; ; ; ; ; We present the results of a comparative study of spread-F signatures over five low-latitude sites: Chiangmai (CGM; 18.8 N, 98.9 E, mag. Lat. 8.8 N), Thailand; Tanjungsari(TNJ; 6.9 S, 107.6 E, mag. Lat. 16.9 S), Indonesia; Palmas (PAL; 10.2 S, 311.8 E, mag. Lat. 0.9 S) and São José Dos Campos (SJC; 23.2 S, 314.1 E, mag. Lat. 14.0 S), Brazil; and Tucumán (TUC; 26.9 S, 294.6 E, mag. Lat. 16.8 S), Argentina. The investigation was based on simultaneous ionograms recorded by an FMCW (frequency modulated continuous-wave) at CGM, an IPS-71 (digital ionosonde from KEL aerospace) at TNJ, a CADI (Canadian Advanced Digital Ionosonde) at PAL and SJC, and an AIS-INGV (Advanced Ionospheric Sounder – Istituto Nazionale di Geofisica e Vulcanologia) at TUC, during the equinoctial periods March–April (R12 = 2.0 and R12 = 2.2) and September–October (R12 = 6.1 and R12 = 7.0) 2009, for very low solar activity. Spread-F signatures were categorized into two types: the range spread-F (RSF) and the frequency spread-F (FSF). The study confirms that the dynamics and the physical processes responsible for these phenomena are actually complicated. In fact, the features that arise from the investigation are different, depending on both the longitude sector and on the hemisphere. For instance, TUC, under the southern crest of the ionospheric equatorial ionization anomaly (EIA), shows a predominance of RSF signatures, while both SJC, under the southern crest of EIA but in a different longitude sector, and CGM, under the northern crest of EIA, show a predominance of FSF signatures. Moreover, the spread-F occurrence over the longitude sector that includes CGM and TNJ is significantly lower than the spread-F occurrence over the longitude sector of PAL, SJC, and TUC.675 223