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Astron. Astrophys. 320, 612-619 (1997)


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Electron acceleration sites in a large-scale coronal structure

K.-L. Klein 1, H. Aurass 2, I. Soru-Escaut 1 and B. Kálmán 3

1 DASOP, CNRS-URA 2080, Observatoire de Paris, Section de Meudon, F-92195 Meudon, France (klein@obspm.fr)
2 Astrophysikalisches Institut Potsdam, Observatorium für solare Radioastronomie, Telegrafenberg A31, D-14473 Potsdam, Germany
(haurass@aip.de)
3 Heliophysical Observatory of the Hungarian Academy of Sciences, P.O. Box 30, Debrecen, Hungary (kalman@tigris.klte.hu)

Received 25 June 1996 / Accepted 21 August 1996

Abstract

Radio observations and interplanetary particle measurements have shown that even in the absence of conspicuous violent processes in the low atmosphere (such as [FORMULA] flares) electrons are accelerated in the corona, most likely at higher altitudes than during flares ([FORMULA] 0.5  [FORMULA] above the photosphere). The paper presents direct evidence on the acceleration sites from a case study of radio, visible light and soft X-ray observations: electrons are repeatedly accelerated in a large-scale coronal structure which is identified with a streamer in coronographic observations. Energy is simultaneously released in an active region near the base of the structure and at a height of [FORMULA][FORMULA], over several hours before the large-scale structure erupts. Energy input is observed in at least two emerging active regions underneath the streamer. The coronal configuration is three-dimensional, overlying a whole quadrant of the Sun. It is argued that the observations trace multiple sites of energy release presumably in current sheets embedded within the streamer, in agreement with scenarios developed for the acceleration of electrons seen in the corona and at 1 AU, and for the evolution of large-scale coronal structures towards eruption.

Key words: Sun: corona – Sun: flares – Sun: magnetic field – Sun: particle emission – Sun: radio radiation – acceleration of particles

Send offprint requests to: K.-L. Klein

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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