We have investigated several CME‐related SEP events with unusually high abundance of He+ relative to He2+ in the energetic particle population which have been observed between 1998 and 2000 with ACE/SEPICA and SOHO/CELIAS. Usually the abundance of He+ is below a few percent whereas at these times the He+/He2+ ratio can be closer to one. Possible sources for He+ are interstellar pickup ions or cold plasma in CME’s. We have investigated in detail the temporal evolution and the energy spectra of these events. We find that the maximum of the He+/He2+ ratio usually coincides with the arrival of the shock or a solar wind structure. This is a strong indication for local acceleration of these ions. The He+ enhancement does not seem to be associated with cold plasma within CME’s itself. Therefore, most probably interstellar pickup ions are the source for the He+ enhancement. Furthermore, the He+/He2+ ratio appears to be consistently lower at higher energies. Also, the observed temporal variability decreases with increasing energy. These two results seem to indicate two different populations for He+ and He2+ with different energy spectra.
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2 September 2003
SOLAR WIND TEN: Proceedings of the Tenth International Solar Wind Conference
17-31 June 2002
Pisa (Italy)
Research Article|
September 02 2003
Relative Abundance Variations of Energetic He+/He2+ in CME Related SEP Events Available to Purchase
A. Galvin;
A. Galvin
*University of New Hampshire, Space Science Center, Durham, 03824
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B. Klecker;
B. Klecker
†Max‐Planck‐Institut für extraterrestrische Physik, P.O. Box 1603, Garching, 85740 Germany
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M. Hilchenbach;
M. Hilchenbach
**Max‐Planck‐Institut für Aeronomie, Max‐Planck‐Str. 2, Katlenburg‐Lindau, 37819 Germany
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P. Bochsler
P. Bochsler
‡University of Bern, Sidler Str. 5, Bern, 3012 Switzerland
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H. Kucharek
E. Möbius
W. Li
C. Farrugia
M. Popecki
A. Galvin
st
B. Klecker
gger
M. Hilchenbach
stast
P. Bochsler
ggers
*University of New Hampshire, Space Science Center, Durham, 03824
†Max‐Planck‐Institut für extraterrestrische Physik, P.O. Box 1603, Garching, 85740 Germany
**Max‐Planck‐Institut für Aeronomie, Max‐Planck‐Str. 2, Katlenburg‐Lindau, 37819 Germany
‡University of Bern, Sidler Str. 5, Bern, 3012 Switzerland
AIP Conf. Proc. 679, 648–651 (2003)
Citation
H. Kucharek, E. Möbius, W. Li, C. Farrugia, M. Popecki, A. Galvin, B. Klecker, M. Hilchenbach, P. Bochsler; Relative Abundance Variations of Energetic He+/He2+ in CME Related SEP Events. AIP Conf. Proc. 2 September 2003; 679 (1): 648–651. https://doi.org/10.1063/1.1618678
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