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SLAC-PUB-12880
Simulation of Cosmic Ray Acceleration, Propagation and
Interaction in SNR Environment
S.H.Lee, T. Kamael and D.C.Ellison2
1. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305
2. Department of Physics, North Carolina State University
Abstract. Recent studies of young supernova remnants (SNRs) with Chandra, XMM, Suzaku and HESS have revealed
complex morphologies and spectral features of the emission sites. The critical question of the relative importance of the
two competing gamma-ray emission mechanisms in SNRs; inverse-Compton scattering by high-energy electrons and
pion production by energetic protons, may be resolved by GLAST-LAT. To keep pace with the improved observations,
we are developing a 3D model of particle acceleration, diffusion, and interaction in a SNR where broad-band emission
from radio to multi-TeV energies, produced by shock accelerated electrons and ions, can be simulated for a given
topology of shock fronts, magnetic field, and ISM densities. The 3D model takes as input, the particle spectra predicted
by a hydrodynamic simulation of SNR evolution where nonlinear diffusive shock acceleration is coupled to the remnant
dynamics (e.g., Ellison, Decourchelle & Ballet [1]; Ellison & Cassam-Chenai [2]; Ellison, Berezhko & Baring [3]). We
will present preliminary models of the Galactic Ridge SNR RX J1713-3946 for selected choices of SNR parameters,
magnetic field topology, and ISM density distributions. When constrained by broad-band observations, our models
should predict the extent of coupling between spectral shape and morphology and provide direct information on the
acceleration efficiency of cosmic-ray electrons and ions in SNRs.
Keywords: Collisionless shocks, supernova remnants, particle acceleration, cosmic rays
INTRODUCTION
This work aims to develop a highly flexible platform for 3D SNR hydro and cosmic ray (CR) simulation, which
is easily expandable to accept new physics, and adaptable to the complex environments of individual supernova
remnants. As a preliminary work in progress, the simulation is tested under toy model configurations, in a cubic
mesh with a relatively low resolution (21x21x21 binning). Several assumptions and simplifications are made in the
physics of cosmic ray acceleration and diffusion. Once the framework becomes mature, however, we can
immediately proceed to perform realistic modeling of any given SNR, match in broad-band with observations, and
extract useful information.
SNR EVOLUTION AND PARTICLE ACCELERATION
The CR-Hydro code we employ in the simulation couples SNR hydrodynamics to cosmic ray acceleration
interactively using a standard SN hydro code (VH-1) together with a semi-analytical CR kinetic model adapted to
nonlinear diffusive shock acceleration (DSA) in non-relativistic shocks (Blasi et al [4]). In each time step the hydro
code generates hydrodynamic parameter sets for the spherically symmetric SNR shells, which are inputted into the
kinetic model to calculate proton and electron spectra in the shells. The changed ratio between energy density and
pressure due to the freshly produced energetic CR population modifies the global effective ratio of specific heats,
which is feedback to the hydro code and used for the next time step. With parameters taken specifically to model RX
J1713.7-3946, the simulation is run for 1000 years in steps of 100 years. Magnetic field self-generation
(amplification) due to the streaming CR protons in the plasma is not yet considered. The pressure term Pc due to CR
protons modifies the shock structure and leads to non-linearity. Parametric thermal injection (i.e., Blasi, Gabici &
Vannoni [5]) is used to set the particle acceleration efficiency. At each time step, proton spectra are obtained for
Contributed to 1st GLAST Symposium, 02/05/2007--2/8/2007, Stanford, CAWork supported in part by US Department of Energy contract DE-AC02-76SF00515
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Lee, S. H.; Kamae, T. & Ellison, D. C. Simulation of Cosmic Ray Acceleration, Propagation And Interaction in SNR Environment, article, October 15, 2007; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc886985/m1/1/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.