EDP Sciences
Free access
Volume 365, Number 2, January II 2001
Page(s) 198 - 203
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20000148

A&A 365, 198-203 (2001)
DOI: 10.1051/0004-6361:20000148

Injection of energetic protons during solar eruption on 1999 May 9: Effect of flare and coronal mass ejection

J. Torsti1 , L. Kocharov1 , D. E. Innes2 , J. Laivola1 and T. Sahla1 .

1  Space Research Laboratory, Department of Physics, University of Turku, Turku 20014, Finland
2  Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany

(Received 7 August 2000 / Accepted 20 October 2000)

A solar energetic particle (SEP) event was observed on 1999 May 9 by the Energetic and Relativistic Nuclei and Electron instrument (ERNE) onboard the Solar and Heliospheric Observatory (SOHO) spacecraft in association with a coronal mass ejection (CME) and X-ray flare at the western limb. Near flare onset the active region coronal loop structure was seen to erupt and simultaneous blue and red shift velocities of the hot plasma were recorded by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument onboard SOHO. We observe for the first time three periods of the SEP injection in a single event: (i) the first, extremely-hard spectrum injection triggered by the passage of the flare initiated coronal (shock) wave; (ii) a moderately-hard spectrum phase starting about half a hour later, proceeding and ceasing concurrently with metric continuum radio burst; (iii) a prolonged soft spectrum injection dominating in the late phase of the event, after about 1.5 h from the first proton production. The CME bow shock acceleration provides a straightforward explanation of the final spectral redressing, whereas the first acceleration seems triggered by the flare. These observations lead us to conclude that the 1999 May 9 SEP event was caused by a combination of coronal and interplanetary acceleration processes contributing with varying importance at different stages of the solar eruption associated with both flare and CME. Comparison with other events suggests that it is a common property of mixed SEP events.

Key words: acceleration of particles -sun: flares -sun: corona -sun: particle emission

Offprint request: L. Kocharov, leon.kocharov@srl.utu.fi

© ESO 2001