Role of Flares and Shocks in Determining Solar Energetic Particle Abundances
Abstract
We examine solar energetic particle (SEP) event-averaged abundances of Fe relative to O and intensity versus time profiles at energies above 25 MeV/nucleon using the SIS instrument on ACE. These data are compared with solar wind conditions during each event and with estimates of the strength of the associated shock based on average travel times to 1 AU. We find that the majority of events with an Fe to O abundance ratio greater than two times the average 5–12 MeV/nuc value for large SEP events (0.134) occur in the western hemisphere. Furthermore, in most of these Fe-rich events the profiles peak within 12 hours of the associated flare, suggesting that some of the observed interplanetary particles are accelerated in these flares. The vast majority of events with Fe/O below 0.134 are influenced by interplanetary shock acceleration. We suggest that variations in elemental composition in SEP events mainly arise from the combination of flare particles and shock acceleration of these particles and/or the ambient medium.
Additional Information
© 2006 by the American Geophysical Union. Received 13 February 2005; revised 6 February 2006; accepted 15 March 2006; published 23 June 2006. H.V.C. was supported at GSFC by a contract with USRA. The work at California Institute of Technology was supported by NASA under grant NAG5-12929. We thank the referees for constructive criticism. Shadia Rifai Habbal thanks Stephen Kahler and the other two referees for their assistance in evaluating this paper.Attached Files
Published - 2006-07.pdf
Supplemental Material - jgra17918-sup-0001-t01.txt
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Additional details
- Eprint ID
- 56015
- Resolver ID
- CaltechAUTHORS:20150324-102418436
- NASA
- NAG5-12929
- Created
-
2015-03-24Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Space Radiation Laboratory
- Other Numbering System Name
- Space Radiation Laboratory
- Other Numbering System Identifier
- 2006-07