Solar coronal streamers observed at 169 MHz with the Nançay East-West radioheliograph |
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| Authors: | F Axisa Y Avignon M J Martres M Pick P Simon |
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| Institution: | (1) Service d'Electronique Physique, Centre d'Etudes Nucléaires de Saclay, France;(2) Meudon Observatory, France |
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| Abstract: | The slowly varying component of the Sun at 169 MHz for the period August 1962 to March 1966 has been studied, using daily data from the East West radioheliograph at Nançay.By relating these radio data to the optical features visible on the solar disc (calcium plages and filaments), this thermal radio-emission can be satisfactorily interpreted as originating in both helmets and active streamers:The radio-sources responsible for this emission are linked to the presence of filaments. Depending on the cases, these filaments are either very far from any calcium plage, or closely associated with them.The cross-sectional area of such sources is often far from having circular symmetry and seems to be closely related to the configuration of the underlying filament itself.In several cases, the altitude of the sources can be estimated, and a typical value of about 270000 km is found. In this respect no significant difference is found between radio-sources related to a filament closely associated with a calcium plage, and those which are related to a filament very far from such plages.At 169 MHz, coronal enhancements provide a relatively small contribution to the slowly varying component.Finally, the observations are used to derive a morphological model for streamers in the medium corona, and several implications of such a model are briefly discussed. |
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