Open AccessEffects of interplanetary transport on derived energetic particle source strengths
Author(s) -
Chollet E. E.,
Giacalone J.,
Mewaldt R. A.
Publication year - 2010
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009ja014877
Subject(s) - physics , adiabatic process , computational physics , mean free path , range (aeronautics) , solar energetic particles , scattering , heliosphere , solar wind , interplanetary medium , interplanetary spaceflight , plasma , nuclear physics , coronal mass ejection , optics , materials science , composite material , thermodynamics
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.