Heidelberg 2006 – scientific programme

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EP: Extraterrestrische Physik

EP 6: Poster

EP 6.8: Poster

Tuesday, March 14, 2006, 14:00–16:30, C

The November 1, 2004 Solar Energetic Particle Event: SOHO/COSTEP observations — •R. Gómez-Herrero, A. Klassen, R. Müller-Mellin, B. Heber, and R. Wimmer-Schweingruber — Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität Kiel, Ohlshausenstr. 40, 24118 Kiel

On November 1, 2004 a 925 km/s partial halo Coronal Mass Ejection (CME) was observed over the west solar limb by LASCO C2 coronagraph on board SOHO. In association with this CME, a solar energetic particle event was detected by the COSTEP/EPHIN instrument. Disk observations and the lack of X-ray flare on the visible hemisphere of the Sun suggest that the source of the event was located on the backside of the Sun, probably in the NOAA active region 10684, more than 30 degrees beyond the west limb. Energetic proton and 4He spectra observed by EPHIN became invariant during the decay phase of the event. The low 4He/1H ratio observed during the event, together with the spectral invariance and the association with a fast CME, are signatures normally found on shock-associated (gradual) events. However they were also accompanied by a moderate 3He enrichment, which was probably related to a 3He-rich seed population provided by the previous intense 3He-rich events starting on October 30. Observational features and possible scenarios to explain particle propagation from the backside source to the near-Earth environment are proposed and discussed.