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The role of interplanetary scattering in western hemisphere large solar energetic particle events

Mason, G. M. and Desai, M. I. and Cohen, C. M. S. and Mewaldt, R. A and Stone, E. C. and Dwyer, J. R. (2006) The role of interplanetary scattering in western hemisphere large solar energetic particle events. Astrophysical Journal, 647 (1). L65-L68. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:MASapjl06

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Abstract

Using high-sensitivity instruments on the ACE spacecraft, we have examined the intensities of O and Fe in 14 large solar energetic particle events whose parent activity was in the solar western hemisphere. Sampling the intensities at low (~273 keV nucleon to the -1) and high (~12 MeV nucleon to the -1) energies, we find that at the same kinetic energy per nucleon, the Fe/O ratio decreases with time, as has been reported previously. This behavior is seen in more than 70% of the cases during the rise to maximum intensity and continues in most cases into the decay phase. We find that for most events if we compare the Fe intensity with the O intensity at a higher kinetic energy per nucleon, the two time-intensity profiles are strikingly similar. Examining alternate scenarios that could produce this behavior, we conclude that for events showing this behavior the most likely explanation is that the Fe and O share similar injection profiles near the Sun, and that scattering in the interplanetary medium dominates the profiles observed at 1 AU.


Item Type:Article
ORCID:
AuthorORCID
Mason, G. M.0000-0003-2169-9618
Cohen, C. M. S.0000-0002-0978-8127
Additional Information:© 2006 The American Astronomical Society. Received 2006 June 16; accepted 2006 July 6; published 2006 August 1. This work was supported by NASA grant NNG04GJ51G at the Johns Hopkins University Applied Physics Laboratory, NASA grant NAG 5-6912 and NSF grant ATM 04-54428 at the California Institute of Technology, and NASA grant NNG05GQ96G and NSF grant ATM 05-55878 at SwRI.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANNG04GJ51G
NASANAG 5-6912
NSFATM-0454428
NASANNG05GQ96G
NSFATM-0555878
Subject Keywords:acceleration of particles; cosmic rays; interplanetary medium; solar flares
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2006-05
Issue or Number:1
Record Number:CaltechAUTHORS:MASapjl06
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:MASapjl06
Alternative URL:http://www.journals.uchicago.edu/ApJ/journal/issues/ApJL/v647n1/20849/brief/20849.abstract.html
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6738
Collection:CaltechAUTHORS
Deposited By: Lindsay Cleary
Deposited On:20 Dec 2006
Last Modified:12 Sep 2017 03:58

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