Articles | Volume 26, issue 13
https://doi.org/10.5194/acp-26-9571-2026
https://doi.org/10.5194/acp-26-9571-2026
Research article
 | 
08 Jul 2026
Research article |  | 08 Jul 2026

Automated detection of low-altitude isolated mesospheric radar echoes using YOLOv8: evidence for an ionospheric “C layer” phenomenon below 60 km altitude?

Yadu Krishnan Krishnakumar, Toralf Renkwitz, and Andreas Ahrens

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Cited articles

Abdu, M. A., Ananthakrishnan, S., Krishnan, B. A., and Massambani, O.: Cosmic ray ionization in the D region at sunrise: Evidence from VLF phase measurements, Radio Sci., 8, 733–736, https://doi.org/10.1029/RS008i008p00733, 1973. a
Al Mudawi, N., Qureshi, A. M., Abdelhaq, M., Alshahrani, A., Alazeb, A., Alonazi, M., and Algarni, A.: Vehicle Detection and Classification via YOLOv8 and Deep Belief Network over Aerial Image Sequences, Sustainability, 15, 14597, https://doi.org/10.3390/su151914597, 2023. a
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Bain, W. C. and Kossey, P. A.: Characteristics of a reflecting layer below the classical D region, J. Geophys. Res.-Space, 92, 12443–12444, https://doi.org/10.1029/JA092iA11p12443, 1987. a, b
Bain, W. C. and May, B. R.: D region electron-density distributions from propagation data, Proceedings of the Institution of Electrical Engineers, 114, https://doi.org/10.1049/piee.1967.0306, 1967. a
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We report on the observations of radar echoes at the lower HF range from the lower part of the ionosphere, below 60 km altitude. The observed echoes are actually seen below and isolated to the generally accepted lowermost ionospheric D region. For the detection of these echoes we employed machine learning techniques for the inspection of 4 years of radar raw data. We derived statistical parameters of their occurrence and hypothesised a connection for galactic cosmic rays as an ionisation source.
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