Ionospheric scintillation observations with radio interferometry |
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| Institution: | 1. Netherlands Foundation for Research in Astronomy, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands;2. Beijing Astronomical Observatory Academia Sinica, Beijing 100080, China;1. Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, China;2. State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing, 100084, China;3. Department of Mechanical Engineering, Imperial College London, Exhibition Road, South Kensington Campus, London, SW7 2AZ, UK;4. Department of Naval Architecture and Marine Engineering, University of Michigan, Ann Arbor, MI, 48109, USA;5. Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID, 83415, USA;6. Transportation and Hydrogen System Center, National Renewable Energy Laboratories, Golden, CO, 80401, USA;7. Department of NanoEngineering, University of California, San Diego, CA, 92093-0448, USA;8. College of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China;9. College of Engineering, China Agricultural University, Beijing, 100083, China;1. Department of Physics, Federal University of Technology, Minna, Nigeria;2. Department of Physics, Federal University of Technology, Akure, Nigeria;3. Department of Mechatronics Engineering, Federal University of Technology, Minna, Nigeria;1. Space Technology Research Center, Tsinghua University, Beijing 100084, China;2. Zhengzhou Information Technology Institute, Zhengzhou 450002, China |
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| Abstract: | Radio astronomical interferometric observations are affected by atmospheric refraction, being particularly sensitive to inhomogeneities in the atmosphere. At frequencies below 2 GHz the influences of the ionosphere are significant in radio astronomy, especially for single dish observations and for connected element interferometry.Analytical expressions for the manifestations of weak ionospheric scintillation in radio interferometric observations, are derived. We indicate which ionospheric scintillation parameters can be derived from radio interferometric measurements. It is shown that the baseline dependence of the observed amplitude scintillation index implies a direct determination of the height of the region of random irregular electron distribution. Furthermore, the linear scale of the irregularities causing scintillation can be determined directly from the baseline dependence of the scintillation index S4. From the mean square phase fluctuations as a function of interferometer baseline, the spatial scale of the irregularities responsible for this effect can also be determined. From a comparison with observational mid-latitude data we find indications that scintillation irregularities occur in the lower parts of the F2-layer. The spatial scale of irregularities causing amplitude scintillation is of the order of about 25 to about 500 metres. Phase scintillations are caused by irregularities with dimensions which are an order of magnitude larger. |
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