Long-Term Radio Scintillation Variations in the Circumsolar Plasma |
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| Authors: | Lotova NA Obridko VN Vladimirskii KV Bird MK Pätzold M Sieber W Güsten R Korelov OA |
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| Institution: | (1) Institute of Terrestrial Magnetism, Ionosphere, and Radio Propagation (IZMIRAN), Russian Academy of Sciences, 142092 Troitsk, Moscow Region, Russia;(2) Lebedev Physical Institute, Russian Academy of Sciences, Leninskii pr. 53, 117924 Moscow, Russia;(3) Radio Astronomy Institute, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany;(4) Institute for Geophysics and Meteorology, University of Cologne, 50923 Cologne, Germany;(5) Scientific Research Institute for Radio Physics (NIRFI), Bolshaya Pechorskaya 25/14, 603600 Nizhnii Novgorod, Russia |
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| Abstract: | Long-term scintillation measurements of the solar wind formation zone at solar elongations ranging from 1°–8° (Sun impact parameters: 4–30 R
 ) were recorded using the water maser source IRC-20431 at the wavelength  =1.35 cm during its annual solar occultations in December 1981–1998. Dramatic changes in the spatial dependence of the scintillation index were recorded over the course of the 11-year solar cycle. Markedly diminished scattering, attributed to a pronounced heliolatitude effect, was observed at the closest solar approach distances in the years around solar activity minimum. From parallel investigations of the solar magnetic field structure it was determined that the field strength at the source of the solar wind streamlines is the governing factor for the solar wind acceleration process. Particularly apparent in the scintillation data during solar activity minimum is the increasing role of the polar coronal holes with their associated open magnetic field structure. The dependence of the solar scattering intensity on heliolatitude fades in the years of high solar activity as the level of scintillations increases at polar latitudes. |
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