Navegando por Autor "Carrasco, Alexander Jose"

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    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.
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    New Findings of the Sporadic E (Es) Layer Development Around the Magnetic Equator During a High-Speed Solar (HSS) Wind Stream Event
    (Advancing Earth and Space Sciences) Resende, Laysa Cristina Araújo; Zhu, Y.; Denardini, Clezio Marcos; Batista, Inez Staciarini; Shi, Jiankui; Moro, Juliano; Chen, Sony Su; Santos, Fredson Conceição; Silva, Ligia Alves da; Andrioli, Vania Fatima; Muella, Marcio Tadeu de Assis Honorato; Fagundes, Paulo Roberto; Carrasco, Alexander Jose; Pillat, Valdir Gil; Wang, Chi; Liu, Z.
    The equatorial (Esq) and blanketing (Esb) sporadic (Es) layers occur due to the EquatorialElectrojet Current (EEJ) plasma instabilities and tidal wind components, respectively. Both Esq and Esb layers can appear concurrently over some Brazilian equatorial regions due to the peculiar geomagnetic field configuration in this sector. Previous works indicate that the inclination angle limit for the Esq occurrence in ionograms is 7°. However, we found evidence that regions more distant can also experience such equatorial dynamics during disturbed periods. In this context, we deeply investigated this EEJ influence expansion effect by analyzing the Esq layers in regions not so close to the magnetic equator during a high-speed solar wind stream event that occurred on May 05 and 06, 2018. To explain these atypical Esq layer occurrences, we considered the Es layer parameters obtained from digital ionosondes over the Brazilian regions, São Luís (dip: 9.5°), and Araguatins (dip: 10.5°). We use magnetometer data and a model named MIRE (E Region Ionospheric Model) to validate this mechanism. The results show that the eastward electric field of the Gradient Drift instability in the EEJ is effective during the magnetic storm main phase in the boundary equatorial magnetic sites, creating the Es q layers. Thus, the EEJ plasma irregularity superimposes the wind shear mechanism, changing the Es layer dynamics during disturbed periods over the magnetic equator boundary sites. Therefore, this work establishes new findings of the EEJ influence expansion dynamics in the Es layer formation over the Brazilian regions, which was considered in MIRE for the first time.