Chollet, E. E. and Giacalone, J. and Mewaldt, R. A. (2010) Effects of interplanetary transport on derived energetic particle source strengths. Journal of Geophysical Research A, 115 . Art. No. A06101. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20100624-090852258
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We study the transport of solar energetic particles (SEPs) in the inner heliosphere in order to relate observations made by an observer at 1 AU to the number and total energy content of accelerated particles at the source, assumed to be near the Sun. We use a numerical simulation that integrates the trajectories of a large number of individual particles moving in the interplanetary magnetic field. We model pitch angle scattering and adiabatic cooling of energetic ions with energies from 50 keV nucleon^(−1) to 100 MeV nucleon^(−1). Among other things, we determine the number of times that particles of a given energy cross 1 AU and the average energy loss that they suffer because of adiabatic deceleration in the solar wind. We use a number of different forms of the interplanetary spatial diffusion coefficient and a wide range of scattering mean-free paths and consider a number of different ion species in order to generate a wide range of simulation results that can be applied to individual SEP events. We apply our simulation results to observations made at 1 AU of the 20 February 2002 solar energetic particle event, finding the original energy content of several species. We find that estimates of the source energy based on SEP measurements at 1 AU are relatively insensitive to the mean-free path and scattering scheme if adiabatic cooling and multiple crossings are taken into account.
|Additional Information:||© 2010 by the American Geophysical Union. Received 4 September 2009; revised 7 December 2009; accepted 13 January 2010; published 2 June 2010. We have greatly benefited from useful discussions of this topic with Randy Jokipii. We appreciate the availability of EPAM, SIS, and ULEIS data from the ACE Science Center and the availability of GOES data from NOAA. The work at University of Arizona was supported in part by NSF under grant ATM0447354. The work at Caltech was supported by NASA under grants NNX8AI11G and NNX06AC21G. Amitava Bhattacharjee thanks Dennis Haggerty and A. Gordon Emslie for their assistance in evaluating this paper.|
|Group:||Space Radiation Laboratory|
|Official Citation:||Chollet, E. E., J. Giacalone, and R. A. Mewaldt (2010), Effects of interplanetary transport on derived energetic particle source strengths, J. Geophys. Res., 115, A06101, doi:10.1029/2009JA014877.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||03 Aug 2010 18:51|
|Last Modified:||04 Mar 2013 22:43|
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