Tese-PPGFA

URI Permanente para esta coleção

https://repositorio.univap.br/handle/123456789/87

Navegar

Navegando Tese-PPGFA por Autor "Batista, Inez Staciarini"

Agora exibindo 1 - 2 de 2
  • Imagem de Miniatura
    Item
    Multi-instrument study of various aspects of equatorialionospheric irregularities over American and African sectors
    (2022-08-02) Fagundes, Paulo Roberto; Pillat, Valdir Gil; Ojeda González, Arian; Silva, Igo Paulino; Batista, Inez Staciarini; Agyei-Yeboah, Ebenezer; Tardelli, Alexandre; São José dos Campos
    This thesis is devoted to the study of ionospheric irregularities observed over Brazil and Africa using different instruments and observational techniques. First, the occurrence of ionospheric irregularities like plasma bubbles, blobs, and Spread-F (typical and atypical have been investigated using all-sky imaging systems and ionosondes located at Araguatins, Jataí, and São José dos Campos. Afterward, GPS-TEC data from 33 receiver stations located in different parts of Brazil and Africa were used in the investigation of ROT (rate of TEC change) phase fluctuations during the Antarctic Sudden Stratospheric Warming (SSW). Electron density measurements from the Swarm constellation have also been employed to aid in the analysis and discussion of some of the results obtained from ionosonde and ASI. The thesis focuses on two main studies. One study was dedicated to exploring the observation of the simultaneous occurrence of ionospheric plasma bubbles and blobs using an all-sky imaging system and the observation of atypical Spread-F on ionograms. Based on these observations, a novel methodology is proposed for the observation and studies of ionospheric plasma blobs using ionosondes. The proposed methodology employed a colocated all-sky imager and ionosonde at Araguatins to observe simultaneously occurring plasma bubbles and blobs and then the corresponding ionograms were analyzed. The characteristics of the echoes on the ionograms were compared with the observations from the OI 630 nm nightglow images from the all-sky imager for when there were no irregularities and when bubbles and/or blobs were present. The results showed that in the presence of bubbles and blobs, Spread-Fs with high-frequency echoes were drawn on the ionograms at almost the same time as the images were taken. The results also showed that the generation of plasma blobs could be influenced by the development of bubbles and that the equatorial ionization anomaly may play a major role in their development. The other focus of the thesis is the study of the effects of the 2019 minor Antarctic SSW event on the generation/suppression of ionospheric irregularities. The critical frequency obtained from the three ionosonde stations at Araguatins, Jataí, and São José dos Campos was used to monitor the ionospheric irregularities during the different phases of the SSW event. Spread-F (Brazil) and ROT phase fluctuations (Brazil, Africa) occurrence at different latitudes during different phases of the event were analyzed. Irregularity occurrence from a similar period in 2018 when no SSW event was recorded in the Antarctic region was also analyzed. The results showed a general decrease in occurrence rates during the peak phase of the event compared to the other phases in 2019. The results also showed a decrease in occurrence rate from the peak phase in 2018 (no SSW) to the peak phase in 2019 (SSW).
  • Imagem de Miniatura
    Item
    Ocorrência e modelagem das camadas e-esporádicas em baixas-latitudes no setor brasileiro
    (2020-02-20) Muella, Marcio Tadeu de Assis Honorato; Fagundes, Paulo Roberto; Tardelli, Alexandre; Pillat, Valdir Gil; Batista, Inez Staciarini; Silva, Vânia Fátima Andrioli Novaes; Conceição-Santos, Fredson; Chagas, Láysa Cristina Araujo Resende; São José dos Campos
    Camadas E-esporádicas (Es) são adensamentos de plasma que se localizam nas alturas da região E entre 90 e 150 km. Elas são compostas principalmente por íons metálicos e são classificadas em oito tipos diferentes associados aos seus mecanismos físicos de formação. O principal mecanismo em baixas latitudes é o cisalhamento dos ventos neutros. Nesse contexto, este estudo analisa os diferentes tipos de camadas Es que aparecem nos registros das ionossondas instaladas nas estações de baixa latitude de São José dos Campos (SJC) e Jataí (JAT) nos meses de abril, junho, setembro e dezembro de 2016. Os resultados mostraram que nessas regiões há a presença de cinco tipos de camadas, “cusp”, “high”, “flat”, “low” e “slant”, sendo os tipos “flat/low” (Esf/l) os mais frequentes. Além disso, o papel dos ventos na formação dessas camadas é investigado usando o Modelo Ionosférico da Região E (MIRE), que incorpora ventos de marés inferidos de medições do radar meteórico de Cachoeira Paulista (CXP). Para isso, são comparadas a densidade eletrônica deduzida do parâmetro de frequência de bloqueio (fbEs) nos ionogramas com a densidade eletrônica simulada pelo MIRE. Como os ventos mostraram-se atípicos e, consequentemente, houve algumas discrepâncias entre os resultados do modelo e as observações, as amplitudes das componentes do vento zonal/meridional foram ajustadas por fatores específicos para cada mês, com o objetivo de quantificar esta discrepância. Outro estudo realizado neste trabalho foi a análise da influência do modo da maré diurna e semidiurna sobre a dinâmica da camada Es do tipo high (Esh). Os resultados mostraram que o padrão de maré e a direção do vento predominante que controlam a formação e a descida da camada Esh são diferentes dependendo do mês de análise, o que sugere a existência de padrões sazonais distintos acontecendo no setor brasileiro.