| Autor: |
Moro, J.1,2,3 (AUTHOR) juliano.moro@inpe.br, Xu, J.1 (AUTHOR), Bageston, J. V.2,3 (AUTHOR), Denardini, C. M.3 (AUTHOR), Andrioli, V. F.1,3 (AUTHOR), Resende, L. C. A.1,3 (AUTHOR), Da Silva, L. A.1,3 (AUTHOR), Li, H.1 (AUTHOR), Liu, Z.1 (AUTHOR), Wang, C.1 (AUTHOR), Schuch, N. J.4 (AUTHOR) |
| Předmět: |
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| Zdroj: |
Journal of Geophysical Research. Space Physics. Dec2023, Vol. 128 Issue 12, p1-13. 13p. |
| Abstrakt: |
Analyses on a complete year of Digisonde data are conducted to investigate the sporadic‐E (Es) layers over Santa Maria (29.7°S, 53.8°W, dip lat.: −37°), Brazil. This region is undergoing a transition from low latitude to midlatitude within the South American Magnetic Anomaly (SAMA), which provides a key motivation to explore their behavior and the associated tidal periodicities. The Es are classified into four types: flat (Esf), low (Esl), high (Esh), and cusp (Esc). The diurnal and seasonal variations of their top (ftEs) and blanketing (fbEs) frequencies and virtual height (h′Es) are examined. The frequency parameters show the presence of intense Es during equinoxes besides summer. It is also remarkable that the higher values of mean h′Es during winter compared to the other seasons during daytime. These observations differ from previous theories about midlatitude Es layers. The diurnal occurrence rates of the Esb types exhibited distinct dependencies on both local time and seasons. The Esh and Esc were observed exclusively during the daytime, with the former dominating the occurrences in all seasons. To investigate any tidal periodicities embedded in the ftEs, fbEs, and h′Es time series, the Lomb‐Scargle technique was employed. The analysis revealed the presence of 24‐, 12‐, 8‐, and 6‐hr periodicities in both fbEs and h′Es when considering the entire year of data. However, when the data are fractioned into seasons, the predominant periodicities were found to be 24‐ and 12‐hr cycles. Furthermore, when considering the different Esb types, the Lomb‐Scargle analysis indicated varying periodicities. Key Points: Intense Es layers are observed in equinoxes besides summer, differing to some extent from previous observations about midlatitude Es layersThe mean height of Es is found to be different from previous investigations, with higher values in winter compared to summerSpectral peaks reveal the 24‐, 12‐, 8‐, and 6‐hr periodicities embedded in the Es parameters' time series measured in Santa Maria [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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