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The dependence of solar energetic particle fluences on suprathermal seed-particle densities

Mewaldt, R. A. and Mason, G. M. and Cohen, C. M. S. (2012) The dependence of solar energetic particle fluences on suprathermal seed-particle densities. In: Space weather : the space radiation environment. AIP Conference Proceedings. No.1500. American Institute of Physics , Melville, NY, pp. 128-133. ISBN 978-0-7354-1114-2.

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Measurements during solar cycle 23 showed that most solar energetic particles (SEPs) are accelerated from a seed-population of suprathermal ions (e.g., >10 keV/nuc) rather than from the bulk solar wind. In this case the SEP fluence should depend on the pre-existing density of suprathermal ions. Lacking near-Sun measurements of suprathermal ion densities we have used ACE/ULEIS daily-average densities of suprathermal Fe at 1 AU during 1998-2005 as a proxy. We find that the maximum Fe daily-average SEP fluences measured by ACE/SIS are apparently limited by the pre-existing suprathermal number density. Similarly, large fluences of Fe in solar energetic particle events only occurred when there was a pre-existing high density of suprathermal Fe. We conclude that in situ suprathermal ion data can play a key role in estimating the probability of large SEP events, or in forecasting all-clear periods.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Mewaldt, R. A.0000-0003-2178-9111
Mason, G. M.0000-0003-2169-9618
Cohen, C. M. S.0000-0002-0978-8127
Additional Information:© 2012 American Institute of Physics. NASA funded this work under grants NNX08AI11G and NNX11A075G at Caltech, and NNX10AT75G at JHU/APL; and subcontracts SA2715-26309 and SA4889-26309 from UC Berkeley under NASA contract NAS5-03131. We are grateful for the availability of SWEPAM data from the ACE Science Center.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:cosmic ray propagation; iron; solar wind
Series Name:AIP Conference Proceedings
Issue or Number:1500
Classification Code:PACS: 96.30.Ys; 96.50.Vg; 96.60.Q-; 96.60.Vg
Record Number:CaltechAUTHORS:20130114-101755528
Persistent URL:
Official Citation:The dependence of solar energetic particle fluences on suprathermal seed-particle densities R. A. Mewaldt, G. M. Mason, and C. M. S. Cohen, AIP Conf. Proc. 1500, 128 (2012), DOI:10.1063/1.4768755
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36347
Deposited On:14 Jan 2013 21:51
Last Modified:09 Nov 2021 23:21

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