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Evidence for a Two-Stage Acceleration Process in Large Solar Energetic Particle Events

Desai, M. I. and Mason, G. M. and Gold, R. E. and Krimigis, S. M. and Cohen, C. M. S. and Mewaldt, R. A. and Mazur, J. E. and Dwyer, J. R. (2007) Evidence for a Two-Stage Acceleration Process in Large Solar Energetic Particle Events. Space Science Reviews, 130 (1-4). pp. 243-253. ISSN 0038-6308. doi:10.1007/s11214-007-9219-x.

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Using high-resolution mass spectrometers on board the Advanced Composition Explorer (ACE), we surveyed the event-averaged ~0.1–60 MeV/nuc heavy ion elemental composition in 64 large solar energetic particle (LSEP) events of cycle 23. Our results show the following: (1) The Fe/O ratio decreases with increasing energy up to ~10 MeV/nuc in ~92% of the events and up to ~60 MeV/nuc in ~64% of the events. (2) The rare isotope ^3He is greatly enhanced over the corona or the solar wind values in 46% of the events. (3) The heavy ion abundances are not systematically organized by the ion’s M/Q ratio when compared with the solar wind values. (4) Heavy ion abundances from C–Fe exhibit systematic M/Q-dependent enhancements that are remarkably similar to those seen in ^3He-rich SEP events and CME-driven interplanetary (IP) shock events. Taken together, these results confirm the role of shocks in energizing particles up to ~60 MeV/nuc in the majority of large SEP events of cycle 23, but also show that the seed population is not dominated by ions originating from the ambient corona or the thermal solar wind, as previously believed. Rather, it appears that the source material for CME-associated large SEP events originates predominantly from a suprathermal population with a heavy ion enrichment pattern that is organized according to the ion’s mass-per-charge ratio. These new results indicate that current LSEP models must include the routine production of this dynamic suprathermal seed population as a critical pre-cursor to the CME shock acceleration process.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle ReadCube access
Desai, M. I.0000-0002-7318-6008
Mason, G. M.0000-0003-2169-9618
Krimigis, S. M.0000-0003-2781-2386
Cohen, C. M. S.0000-0002-0978-8127
Mewaldt, R. A.0000-0003-2178-9111
Additional Information:© 2007 Springer Science+Business Media B.V. Received: 7 December 2006. Accepted: 19 May 2007. Published online: 18 July 2007 Work at SwRI was partially supported by NASA grant NNG05GQ94G and NSF grant ATM-0555878. Work at Caltech was supported by NASA grant NAG5-12929.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Sun : energetic particles; Sun : coronal mass ejections; Sun : flares
Issue or Number:1-4
Record Number:CaltechAUTHORS:20100910-144222641
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Official Citation:Desai, M.I., Mason, G.M., Gold, R.E. et al. Space Sci Rev (2007) 130: 243.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19875
Deposited By: Tony Diaz
Deposited On:16 Sep 2010 22:17
Last Modified:08 Nov 2021 23:55

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