D-region electron density diurnal changes observed in association with the PCA event of July 1974 |
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| Affiliation: | 1. Mbarara University of Science and Technology, Department of Physics, Mbarara P. O. Box 1410, Uganda;2. Muni University, Department of Physics, Arua P.O. Box 725, Uganda;3. Swedish Institute of Space Physics, Uppsala, Sweden;4. South African National Space Agency, Hospital Street, Hermanus P. O. Box 32, South Africa;5. Rhodes University Makhanda, Department of Physics and Electronics, 6139, Eastern Cape, P. O. Box 6140, South Africa;1. Defence Science and Technology Group, Edinburgh 5111, Australia;2. The University of Adelaide, Adelaide 5005, Australia;1. Department of Space Environment, Institute of Basic and Applied Sciences, Egypt-Japan University of Science and Technology (E-JUST), New Borg El-Arab City, Alexandria 21934, Egypt;2. Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Nagoya 464-8601, Japan;3. Department of Mathematics, Institute of Basic and Applied Sciences, Egypt-Japan University of Science and Technology (E-JUST), New Borg El-Arab City, Alexandria 21934, Egypt;4. Department of Engineering Physics and Mathematics, Faculty of Engineering, Tanta University, Tanta 31527, Egypt;5. Department of Physics, Faculty of Science, Helwan University, Helwan, Cairo 11795, Egypt |
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| Abstract: | Well defined diurnal phase and amplitude deviations of very low frequency radio signals propagation were detected during the solar proton event that occurred from 3 to 8 July 1974. Phase advances observed on signals transmitted from GBR (U.K.), received at Atibaia (Brazil) and at Inubo Radio Observatory (Japan), were compared with simultaneous NWC (Australia) transmissions received at Atibaia, and at Syowa Station (Antarctica). Emphasis was given to the propagation paths NWC-Atibaia and NWC-Syowa, because both propagate completely in the southern hemisphere, crossing regions where the Earth's magnetic field behaves anomalously. The comparison allowed the determination of parameters typical of the D-region at a given height in the lower ionosphere, for geomagnetic regions defined through the McLlwain parameter(L). An exponential model was adopted to fit the vertical distribution of the diurnal electron density. The experimental results showed a delayed contribution to the total ionization observed which was attributed to a slow precipitation of energetic particles in the South Atlantic Geomagnetic Anomaly region. |
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