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| Titel |
Interplanetary fast forward shocks and energetic storm particle events above 1.5 MeV |
| VerfasserIn |
K. Huttunen-Heikinmaa, E. Valtonen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 2 ; Nr. 27, no. 2 (2009-02-17), S.767-779 |
| Datensatznummer |
250016412
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| Publikation (Nr.) |
 copernicus.org/angeo-27-767-2009.pdf |
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| Zusammenfassung |
| Interplanetary (IP) shock passages are usually identified by abrupt
changes in the plasma parameters, but sometimes they are also associated
with energetic storm particles (ESPs). The maximum observed energies
of ESPs usually reach a few MeVs per nucleon and occasionally even
a few hundred MeVs per nucleon. We have carried out a statistical
study of ESP events observed by SOHO/ERNE above 1.5 MeV during the
seven-year period between May 1996 and April 2003. In the first stage,
we gathered a comprehensive database of IP shock candidates using
several ready-made shock lists. We defined a qualitative classification
for the ESP signals and studied their association with fast forward
shocks. We present a survey of the overall statistics of ESP associations
with fast forward shocks and the yearly amount of the shocks and associated
ESP events during the 7-year study period. Our most important findings
are that only 40% of the observed interplanetary fast forward shocks
accelerate ESPs to energies greater than 1.5 MeV and that the high-energy
ESP-effectiveness of the fast forward shocks has a solar cycle dependence.
The yearly ESP-effectiveness varied from 11%, in May 1996–April 1997 (~activity minimum), to 53%
in May 2000–April 2001 (~activity maximum). We also performed a quantitative
analysis of the proton power law spectra at the time of the shock
passage. We found that the average spectral index of ESPs was −3.6
with the standard deviation of the distribution of 1.3. The ESP events
had significantly larger power law factors than the reference spectra,
calculated every day at a certain time for comparison. |
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