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Elemental Fractionation in Small Solar Energetic Particle Events

Slocum, P. L. and Stone, E. C. and Leske, R. A. and Christian, E. R. and Cohen, C. M. S. and Cummings, A. C. and Desai, M. I. and Dwyer, J. R. and Mason, G. M. and Mazur, J. E. and Mewaldt, R. A. and von Rosenvinge, T. T. and Wiedenbeck, M. E. (2003) Elemental Fractionation in Small Solar Energetic Particle Events. Astrophysical Journal, 594 (1). pp. 592-604. ISSN 0004-637X. doi:10.1086/376755.

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Using the Solar Isotope Spectrometer on the Advanced Composition Explorer (ACE), we have measured the 11.0-21.8 MeV nucleon^(-1) heavy (Z ≥ 6) element abundances of 39 small solar energetic particle (SEP) events that occurred between 1998 April 3 and 2002 February 26. Using He isotope data from the Ultra-Low-Energy Isotope Spectrometer on ACE, we have classified the events according to their 0.5-2.0 MeV nucleon^(-1) ^3He/^4He ratios. We find that their average heavy-element composition is similar to that of either large gradual events or ^3He-rich events, depending on their ^3He/^4He ratio. As seen in recent studies of small SEP events, we find that the heavy-element intensities relative to C increase with the ^3He/^4He ratios. The dependence of the heavy-element abundances on first ionization potential (FIP) has been derived, using a model consisting of a power law in Q/M (and Z) times a step function in FIP. We report the magnitude of the FIP factor in each event and find that it varies from ~2 to 7 with no clear dependence on the ^3He/^4He ratio.

Item Type:Article
Related URLs:
URLURL TypeDescription
Stone, E. C.0000-0002-2010-5462
Leske, R. A.0000-0002-0156-2414
Christian, E. R.0000-0003-2134-3937
Cohen, C. M. S.0000-0002-0978-8127
Cummings, A. C.0000-0002-3840-7696
Desai, M. I.0000-0002-7318-6008
Mason, G. M.0000-0003-2169-9618
Mewaldt, R. A.0000-0003-2178-9111
Wiedenbeck, M. E.0000-0002-2825-3128
Additional Information:© 2003 American Astronomical Society. Received 2003 January 13; accepted 2003 May 5. This research was supported by NASA at Caltech (under grant NAG5-6912), JPL, GSFC, The Aerospace Corporation (under NASA Cooperative Agreement 26979B), and the University of Maryland (under grant PC-251429). The authors thank R. E. Gold, D. K. Haggerty, and S. E. Hawkins for providing the electron and ion intensities, which were useful in this analysis. We thank C. W. Smith, H. Qiang, and R. M. Skoug for providing information about the interplanetary conditions relevant to this study. We are also grateful to H. V. Cane for helpful discussions related to this work.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Goddard Space Flight CenterUNSPECIFIED
Aerospace CorporationUNSPECIFIED
University of MarylandPC-25142
Subject Keywords:Sun: flares; Sun: particle emission
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2003-45
Issue or Number:1
Record Number:CaltechAUTHORS:20140827-091516862
Persistent URL:
Official Citation:Elemental Fractionation in Small Solar Energetic Particle Events P. L. Slocum et al. 2003 ApJ 594 592
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48968
Deposited By: Ruth Sustaita
Deposited On:27 Aug 2014 17:47
Last Modified:10 Nov 2021 18:38

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