Análise estatística espacial dos eventos de cintilação ionosférica no Brasil
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2021-03-05
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Universidade Estadual Paulista (Unesp)
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A ionosfera é o principal fator que influencia na acurácia do posicionamento de usuários que possuem receptores de apenas uma frequência. Sabe-se que a ionosfera afeta o sinal GNSS de modo dispersivo e muito dinâmico, variando de acordo com a atividade solar, localização geográfica, horas do dia ou ainda de acordo com sazonalidade. Na região brasileira a ionosfera se comporta de modo distinto devido atuação de fenômenos físicos que influenciam a ionosfera. Entre os efeitos causados nos sinais GNSS pela ionosfera destaca-se a cintilação ionosférica. A cintilação ionosférica é um dos efeitos que mais se busca solução para mitigação, haja vista que afeta inúmeras atividades que envolvam posicionamento, como agricultura de precisão, navegação aérea dentre outros. Assim, devido sua importância e particularidade a cintilação ionosférica tem sido amplamente estudada e de relevância não só para o meio acadêmico, mas também para indústrias e outros seguimentos. Neste documento é apresentada uma revisão de literatura abordando os fenômenos físicos que propiciam a ocorrência de cintilação ionosférica. Também são apresentadas análises a respeito das variações na ocorrência de cintilação ionosférica. Para tais análises foram utilizadas técnicas baseadas na porcentagem de ocorrência de cintilação ionosférica, tanto em fase quanto em amplitude, dado um determinado limiar, bem como técnicas estatísticas. A partir dos dados da rede GNSS NavAer, abrangendo o período de março de 2011 a dezembro de 2018, obteve-se que para a cintilação ionosférica em amplitude os maiores picos ocorreram no ano de 2013/2014, entre as 22h e 4h UTC e nos meses de outubro a março, sendo novembro o mês com maior ocorrência. Já para a cintilação em fase, os maiores picos anuais foram também em 2013/2014 nos meses de outubro a março. Considerando as frequências, obteve-se que os sinais GNSS são mais afetados pela cintilação em amplitude na frequência L5 do que em L1 e L2, e na cintilação em fase temos o mesmo padrão: maior ocorrência em L5 e menor ocorrência em L1. Também se observou que a correlação entre a cintilação em amplitude e cintilação em fase pode chegar a 0,80 quando ocorrem em magnitudes altas.
The ionosphere is the main factor that influences the accuracy of the positioning of users who have receivers of only one frequency. It is known that the ionosphere affects the GNSS signal in a dispersive and very dynamic way, varying according to solar activity, geographic location, hours of the day or even according to seasonality. In the Brazilian region, the ionosphere has a differently behavior due to the performance of physical phenomena that influence the ionosphere. Among the effects caused on the GNSS signals by the ionosphere, ionospheric scintillation stands out. It is one topic of great interest for investigation because it affects numerous activities that involve positioning, such as precision agriculture, air navigation, among others. Thus, due to its importance and particularity, ionospheric scintillation has been widely studied and of relevance not only for the academic environment, but also for agriculture industries, aviation companies and lot of other segments. This document presents a review addressing the physical phenomena that lead to the occurrence of ionospheric scintillation. Analyzes of variations in the occurrence of ionospheric scintillation are also presented. For such analyzes, techniques were used based on the percentage of occurrence of ionospheric scintillation, both in phase and in amplitude, given a certain threshold, as well as statistical techniques. From the data from the GNSS NavAer network, between March/2011 and December/2018 it was obtained that for the amplitude ionospheric scintillation the biggest peaks occurred in the year 2013 and2014, between 22h and 4h UTC and in the months of October to March, being November the month with the highest occurrence. As for the phase scintillation, the biggest annual peaks were also in 2013 and 2014 in the months of October to March. Considering the frequencies, it was found that the scintillation performs differently on GNSS signals and the L5 frequency is more affected by amplitude and phase scintillation than in L1 and L2. It was also observed that the amplitude scintillation and phase scintillation are strong correlated and this correlation can reach 0,80 when this occurrence has higher values.
The ionosphere is the main factor that influences the accuracy of the positioning of users who have receivers of only one frequency. It is known that the ionosphere affects the GNSS signal in a dispersive and very dynamic way, varying according to solar activity, geographic location, hours of the day or even according to seasonality. In the Brazilian region, the ionosphere has a differently behavior due to the performance of physical phenomena that influence the ionosphere. Among the effects caused on the GNSS signals by the ionosphere, ionospheric scintillation stands out. It is one topic of great interest for investigation because it affects numerous activities that involve positioning, such as precision agriculture, air navigation, among others. Thus, due to its importance and particularity, ionospheric scintillation has been widely studied and of relevance not only for the academic environment, but also for agriculture industries, aviation companies and lot of other segments. This document presents a review addressing the physical phenomena that lead to the occurrence of ionospheric scintillation. Analyzes of variations in the occurrence of ionospheric scintillation are also presented. For such analyzes, techniques were used based on the percentage of occurrence of ionospheric scintillation, both in phase and in amplitude, given a certain threshold, as well as statistical techniques. From the data from the GNSS NavAer network, between March/2011 and December/2018 it was obtained that for the amplitude ionospheric scintillation the biggest peaks occurred in the year 2013 and2014, between 22h and 4h UTC and in the months of October to March, being November the month with the highest occurrence. As for the phase scintillation, the biggest annual peaks were also in 2013 and 2014 in the months of October to March. Considering the frequencies, it was found that the scintillation performs differently on GNSS signals and the L5 frequency is more affected by amplitude and phase scintillation than in L1 and L2. It was also observed that the amplitude scintillation and phase scintillation are strong correlated and this correlation can reach 0,80 when this occurrence has higher values.
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Climatologia, Cintilação ionosférica, Sinais GNSS, Climatology, Ionospheric scintillation, GNSS Signals