The outer solar corona during the declining portion of the solar activity cycle |
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| Affiliation: | 1. Center for mathematical Plasma Astrophysics, Mathematics Department, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven, Belgium;2. Plasma Dynamics Group, Department of Automatic Control and Systems Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, UK;3. Plasma Dynamics Group, School of Mathematics and Statistics, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK;4. Investigadores por México-CONACYT, Servicio de Clima Espacial Méxio, Laboratorio Nacional de Clima Espacial, Instituto de Geofísica, Unidad Michoacán, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro 8701, Ex-Hacienda de San José de la Huerta, 58190 Morelia, Michoacán, Mexico;5. School of Information Technology, Deakin University, Melbourne 3125, Australia;6. Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK;7. Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C3, Cd. Universitaria, 5840 Morelia, Michoacán, Mexico |
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| Abstract: | Some hitherto unpublished observations of the coronal radio scattering made in Sydney during 1962 are combined with observations made at various observatories in the two year interval 1960–1962 to deduce the dependence of scattering on solar activity in the range of angular separations 20–80 R⊙.During a period of declining solar activity, the magnitude of the scattering has decreased by a factor of three, the anisotropy in the scattered distributions has been markedly reduced, the radial gradient of scattering in the Sun's equatorial plane has remained close to −1.4 and the shape of the scattering corona has retained approximately the same degree of ellipticity.The interpretation of the observed radial variation of scattering suggests a discrepancy between the radio and optical values of electron density close to the Sun. This may be resolved by assuming that the irregular component of electron density changes from a small fraction of the total at 5R⊙ to dominate the corona at angular distances greater than 50 R⊙.A comparison is made between these scattering results and those derived from the observations of decametric Jupiter bursts, if these are regarded as the manifestations of a similar scattering process in operation at distances greater than 1 a.u. from the Sun. |
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