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Astron. Astrophys. 348, 271-285 (1999)

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Flare-associated energetic particles in the corona and at 1 AU

K.-L. Klein 1, E.L. Chupp 2, G. Trottet 1, A. Magun 3, P.P. Dunphy 2, E. Rieger 4 and S. Urpo 5

1 Observatoire de Paris, Section de Meudon, DASOP, CNRS-UMR 8645, F-92195 Meudon, France
2 University of New Hampshire, Physics Department and Space Science Center, Durham, NH 03824, USA
3 University of Bern, IAP, Sidlerstrasse 5, CH-3012 Bern, Switzerland
4 Max-Planck-Institut für Extraterrestrische Physik, D-85740 Garching bei München, Germany
5 Metsähovi Radio Observatory, Metsähovintie 114, FIN-02540 Kylmälä, Finland

Received 17 July 1998 / Accepted 20 April 1999

Abstract

It is widely believed that the longest lasting and most energetic solar energetic particle events (SEPs) observed in interplanetary space result from acceleration by the bow shocks of coronal mass ejections (CMEs). Using gamma-ray, X-ray and radio diagnostics of interacting particles and spaceborne and ground-based detection of [FORMULA]20 MeV protons at 1 AU during two large events (1989 September 29 and October 19), we demonstrate that time-extended acceleration processes in the low and middle corona, far behind the CME, leave their imprints in the proton intensity time profiles in interplanetary space for one to several hours after the onset of the flare: (1) New increases of [FORMULA]20 MeV proton fluxes at 1 AU can be traced back to episodes of coronal acceleration. (2) Increasing richness of relativistic protons observed at 1 AU in the course of the SEPs is associated with new coronal particle injection after the impulsive phase. (3) Particle injection sites enabling a rapid access to the well-connected magnetic field line, as required by the SEP time profile, exist in the middle corona even if the nominal H[FORMULA] flare location is far away. These findings suggest that contrary to the prevalent view acceleration processes in the low and middle corona supply both interacting and at least part of the interplanetary particles. The association of the most proton-rich component of the SEPs with delayed low-frequency radio emission is consistent with ionization state studies of SEPs, in that both require acceleration in a tenuous plasma. We conclude that the complexity of the corona provides the ingredients for the acceleration of particles and their injection into a large range of heliocentric angles. The CME may play the role of a trigger or even contribute to the buildup of magnetic stresses in the corona, but its bow shock is not the main accelerator of the high-energy protons.

Key words: Sun: activity – Sun: corona – Sun: flares – Sun: particle emission – Sun: radio radiation

Send offprint requests to: K.-L. Klein (Ludwig.klein@obspm.fr)

This article contains no SIMBAD objects.

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© European Southern Observatory (ESO) 1999

Online publication: July 16, 1999
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