Types of ionospheric scintillations in southern mid-latitudes during the last sunspot maximum |
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| Institution: | 1. Department of Physics, University of Lagos, Akoka, Yaba, Lagos, Nigeria;2. International Centre for Theoretical Physics, Trieste, Italy;3. Department of Physics, Lagos State University, Ojo, Lagos, Nigeria;4. Department of Applied Physics, S. V. National Institute of Technology, Surat, India;5. Centre for Atmosph. Research, National Space Research and Development Agency, Ayingba, Nigeria;6. Institute for Scientific Research, Boston College, Chestnut Hill, MA, USA;1. Department of Physics, University of Lagos, Akoka, Yaba, Lagos, Nigeria;2. Institute of Maritime Studies, University of Lagos, Akoka, Yaba, Lagos, Nigeria;3. Institute for Scientific Research, Boston College, Chestnut Hill, MA, USA;4. International Centre for Theoretical Physics, Trieste, Italy;5. W.B. Hanson Centre for Space Sciences, University of Texas at Dallas, Richardson, TX, USA;1. Sharjah Academy for Astronomy, Space Sciences and Technology, University of Sharjah, University City, Sharjah, United Arab Emirates;2. Department of Applied Physics and Astronomy, University of Sharjah, University City, Sharjah, United Arab Emirates;1. Nanjing University of Information Science and Technology, Jiangsu 210044, China;2. National Centre for Space Weather, China Meteorological Administration, Beijing 100081, China;3. Wuhan University, Hubei 430072, China |
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| Abstract: | A 5-yr study (1987–1992) has been undertaken at a southern mid-latitude station, Brisbane (35.6°S invariant latitude) on scintillation occurrences in radio-satellite transmission (at a frequency of 150 MHz) from polar orbit Transit satellites, within a sub-ionospheric invariant latitude range 20–55°S. Over 7000 recorded passes were used to define the spatial and temporal occurrence pattern of different types of scintillation events. Two predominant scintillation types were found: so-called type P (associated with a scintillation patch close to the magnetic zenith) and type S (characteristic of the equatorward edge of auroral scintillation oval). Type S was by far the most frequent during sunspot maximum (1988–1992), with sharp occurrence peaks in the summer-autumn period. Its seasonal occurrence showed a high degree of correlation (correlation coefficient r = 0.8) with the seasonally averaged 10.7 cm solar radio flux. This type occurred mainly at night-time except in austral summer where 40% of scintillations were detected in daytime, coinciding with the well-known summer peak of sporadic-E occurrence. Type P was more predominant during a year (1987) of ascending sunspot activity but decreased to a much lower level during the sunspot maximum. |
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