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Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand
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- PublicationRestrictedEquinoctial spread-F occurrence at low latitudes in different longitude sectors under moderate and high solar activity(2017-11)
; ; ; ; ; ; ; ; ; ; ;; ; ; ;A comparative study aimed to investigate the equatorial and low-latitude spread-F occurrences for moderate solar activity (MSA) and high solar activity (HSA), was carried out considering concurrent observations made in some ionospheric stations, which identify three separate longitudinal sectors: Chiang Mai (CGM; 18.8 ° N, 98.9 ° E, mag. Lat. 13.2 ° N) and Chumphon (CPN; 10.7 ° N, 99.4 ° E, mag. Lat. 3.2 ° N), Thailand; Palmas (PAL; 10.2 ° S, 311.8 ° E, mag. Lat. 0.9 ° S) and Sao Jose dos Campos (SJC; 23.2 ° S, 314.1 ° E, mag. Lat. 14.0 ° S), Brazil; Tucuman (TUC; 26.9 ° S, 294.6 ° E, mag. Lat. 16.8 ° S), Argentina. Spread-F phenomena recorded during the equinoctial months of September and October 2010, March and April 2011, for MSA, March and April 2014, September and October 2014, for HSA, were classified in two different modes: range spread-F (RSF) and frequency spread-F (FSF). The satellite trace (ST) occurrence was also investigated as possible precursor of spread-F events. When comparing the results of equatorial (CPN and PAL) and low-latitude (CGM, SJC, and TUC) stations, some common features independently of the solar activity emerge: (1) a prevalence of RSF signatures is observed in the time interval 20:00–03:00 LT, while FSF occurrences prevail in the time interval 03:00–06:00 LT; (2) STs are confirmed to be a possible precursor of RSF occurrences. For HSA, at equatorial latitudes, spread-F occurrences in the Thai sector (CPN) are higher than those observed in the Brazilian sector (PAL). When comparing the results of low-latitude stations of CGM, SJC, and TUC some unusual aspects characterizing the morphology of spread-F occurrences emerge: (1) contrary to the Thai and Argentine sectors, in the Brazilian sector (SJC), RSF and FSF appearances in September, for HSA, are observed with relatively long persistence times between about 03:00-06:00 LT and 01:00-03:00 LT respectively, while balanced RSF and FSF occurrences with short persistence times are observed for months for MSA; (2) a prevalence of FSF at CGM during the first half of September for MSA, never observed in the Brazilian and Argentine areas. During years of LSA and MSA common morphological aspects are found at CGM and SJC, that is a predominance of FSF, with the lowest persistence times characterizing SJC. This suggests that the low-latitude behaviour of spread-F occurrences, under different levels of solar activity, at least in the longitude sectors here analysed, can be to a some extent generalized.247 7 - 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.675 224