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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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.
|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|
|Subject Keywords:||acceleration of particles; cosmic rays; interplanetary medium; solar flares|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Lindsay Cleary|
|Deposited On:||20 Dec 2006|
|Last Modified:||26 Dec 2012 09:24|
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