Navegando por Autor "Batista, Paulo Prado"

Agora exibindo 1 - 2 de 2
  • Imagem de Miniatura
    Item
    Effects of the Northern Hemisphere sudden stratospheric warmings on the Sporadic-E layers in the Brazilian sector
    (Elsevier) Fontes Neto, Pedro Alves; Muella, Tadeu de Assis Honorato; Resende, Laysa Cristina Araújo; Jesus, Rodolfo de; Fagundes, Paulo Roberto; Batista, Paulo Prado; Pillat, Valdir Gil; Tardelli, Alexandre; Andrioli, Vania F.
    Tidal and Planetary Wave (PWs) amplitudes are strongly influenced by Sudden Stratospheric Warming (SSW) events. A nonlinear interaction between the tidal winds and planetary waves during the SSW may contribute to the intensification of sporadic-E (Es) layers in the lower thermosphere. This work investigated the relationship between SSW events in the Northern Hemisphere and the Es layer occurrence at low latitudes in the Brazilian sector. We used data from digital ionosondes installed in the observatories of Araguatins (ARA, 5.65◦ S; 48.12◦ W; dip lat. − 5.44◦) and S ̃ao Jos ́e dos Campos (SJC, 23.18◦ S; 45.89◦ W; dip lat. − 21.37◦) to analyze the Es layers. Additionally, we used the temperature, zonal wind, and PWs data at high latitudes in the Northern Hemisphere during the major SSW event that occurred in February/2018 and during the events of Dec/2018–Jan/2019 and Dec/2020–Jan/2021. The results showed a maximum frequency peak of 20 MHz (~5 × 106 electrons.cm− 3) at ARA and SJC during these SSW events. The large values of ftEs, fbEs, and electronic densities were observed between 100 and 115 km height in the Esf/l type layers during daytime or nighttime periods. The results also showed that the number of large values of ftEs, fbEs, and electronic density of the Es layer was much higher in ARA than in SJC, in general. The wavelet power spectrum analyses of the ftEs and fbEs showed a periodicity of 2- days before and after the central day of the SSWs events at the station of ARA, with three prominent peaks in the 2018/2019 event. At the SJC station the quasi-2-day periodicity in the wavelet analyses of the ftEs was observed after the central day in all three SSW events, with a peak before the central day during the 2020/2021 event.
  • Imagem de Miniatura
    Item
    Effects of the terdiurnal tide on the sporadic E (Es) layer development at low latitudes over the Brazilian sector
    (European Geosciences Union) Fontes, Pedro Alves; Muella, Marcio Tadeu De Assis Honorato; Resende, Laysa Cristina Araújo; Andrioli, Vânia Fátima; Fagundes, Paulo Roberto; Pillat, Valdir Gil; Batista, Paulo Prado; Carrasco, Alexander Jose
    Sporadic E (Es) layers are patches of high ionization observed at around 100–140 km height in the E region. Their formation at low latitudes is primarily associated with the diurnal and semidiurnal components of the tidal winds via the ion convergence driven by the wind shear mechanism. However, recent studies have shown the influence of other tidal modes, such as the terdiurnal tide. Therefore, this work investigates the effect of terdiurnal tide-like oscillations on the occurrence and formation of the Es layers observed over Palmas (10.17∘ S, 48.33∘ W; dip lat. −7.31∘), a low-latitude station in Brazil. The analysis was conducted from December 2008 to November 2009 by using data collected from CADI (Canadian Advanced Digital Ionosonde). Additionally, the E Region Ionospheric Model (MIRE) was used to simulate the terdiurnal tidal component in the Es layer development. The results show modulations of 8 h periods on the occurrence rates of the Es layers during all seasonal periods. In general, we see three well-defined peaks in a superimposed summation of the Es layer types per hour in summer and autumn. We also observed that the amplitude modulation of the terdiurnal tide on the Es occurrence rates minimizes in December in comparison to the other months of the summer season. Other relevant aspects of the observations, with complementary statistical and periodogram analysis, are highlighted and discussed.