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Seed populations for large solar particle events of cycle 23

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 Dwyer, J. R. and Mazur, J. E. (2008) Seed populations for large solar particle events of cycle 23. In: Particle Acceleration and Transport in the Heliosphere and Beyond: 7th Annual International Astrophysics Conference. AIP Conference Proceedings. No.1039. American Institute of Physics , Melville, NY, pp. 124-130. ISBN 9780735405660.

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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 rare isotope ^3He is greatly enhanced over the corona or the solar wind values in 46% of the events. (2) 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. (3) Heavy ion abundances from C-Fe exhibit systematic M/g-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:Book Section
Related URLs:
URLURL TypeDescription
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:© 2008 American Institute of Physics. Work at SwRI is partially supported by NSF grants ATM-0550960 and ATM-0551127 and NASA grants: NNG05GM88G, NNG05GQ94G, NNX07AC12G, NNX07AG85G, NNX07AP69G, and NNX08AK87G. We thank the following organizations for permission to publish copyrighted material: Elsevier (Fig. 2, from [12]); and American Astronomical Society (Fig. 1 from [15] and Fig. 3 from 10]).
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Solar Energetic Particles; Particle Acceleration; Sun — Solar Cycle
Series Name:AIP Conference Proceedings
Issue or Number:1039
Classification Code:PACS: 96.50.e; 96.50.Pw;
Record Number:CaltechAUTHORS:20090526-130719139
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14301
Deposited On:27 May 2009 18:17
Last Modified:08 Nov 2021 23:10

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