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ORIGINAL RESEARCH article

Front. Astron. Space Sci.
Sec. Space Physics
Volume 12 - 2025 | doi: 10.3389/fspas.2025.1535186

Study of Height-Spread Sporadic-E (HSEs) Layers Observed in the South American Magnetic Anomaly (SAMA)

Provisionally accepted
Juliano Moro Juliano Moro 1,2*Jiyao Xu Jiyao Xu 1José Valentin Bageston José Valentin Bageston 2Ligia Alves Da Silva Ligia Alves Da Silva 1,3Laysa Cristina Araújo Resende Laysa Cristina Araújo Resende 1,3Clezio Marcos De Nardin Clezio Marcos De Nardin 3Vania Fatima Andrioli Vania Fatima Andrioli 1,3Angela Machado Santos Angela Machado Santos 1,3Giorgio Picanço Giorgio Picanço 4Hui Li Hui Li 1Liu Zhengkuan Liu Zhengkuan 1Chi Wang Chi Wang 1Nelson Jorge Schuch Nelson Jorge Schuch 5
  • 1 State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences (CAS), Beijing, Beijing Municipality, China
  • 2 Southern Space Coordination - COESU/INPE, Santa Maria, Brazil
  • 3 National Institute of Space Research (INPE), São José dos Campos, Brazil
  • 4 Research and Development Institute, University of Vale of Paraíba (IP&D/UNIVAP), São José dos Campos, Brazil
  • 5 Collaborator Researcher UFSM-INPE, Santa Maria, Brazil

The final, formatted version of the article will be published soon.

    Spread echoes from the E-region observed in ionograms obtained at high latitudes are generally classified as auroral sporadic-E (Esa) layers. These layers have also been detected in nighttime ionograms collected at some ionospheric stations in the South American Magnetic Anomaly (SAMA) region in Brazil during the recovery phases of geomagnetic storms. However, similar echoes have also been observed in the SAMA during geomagnetically quiet periods or daytime, which are not caused by energetic particle precipitation. Therefore, investigating the occurrence of these spread echoes over a longer period, rather than focusing solely on case studies, has become important. Thus, this study aims to analyze the occurrences of spread echoes from the E-region, referred to here for the first time as "Height-Spread Es (HSEs) layers". The analysis is based on Digisonde data obtained at the Santa Maria station (29.7° S, 53.8° W, ~22.000 nT) in Brazil over one year (2019/2020). The study initially presents examples of these traces on ionograms and then examines their occurrence rates over several time intervals (hours, months, seasons). Among other findings, the statistical analysis reveals that the occurrence rate of HSEs layers is 9,8% during the analyzed period. The HSEs layers appeared predominantly at night and under geomagnetically quiet conditions. Most HSEs layers lasted between 1 hour and 3 hours 30 minutes, with a peak incidence during November, December, and January. Finally, the study discusses the most likely mechanisms responsible for HSEs layer formation, considering the geomagnetic conditions and time of their detection on ionograms.

    Keywords: Sporadic-E layer, HSEs layer, Esa Layer, Sama, Geomagnetic Storm, Digisonde, Radiation Belt Storm Probes

    Received: 27 Nov 2024; Accepted: 10 Jan 2025.

    Copyright: © 2025 Moro, Xu, Bageston, Da Silva, Resende, De Nardin, Andrioli, Santos, Picanço, Li, Zhengkuan, Wang and Schuch. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Juliano Moro, State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences (CAS), Beijing, 100190, Beijing Municipality, China

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