Computational Astrophysics

Introduction
Cosmic rays (CR) are important in a number of astrophysical situations, including stellar winds, supernovae, cluster shocks and jets from active galactic nuclei. CR's not only produce observable radiation but also contribute to the energetics. How CRs are accelerated is a topic of great interest for understanding the observed CR spectrum and the contribution of CRs to astrophysical systems. The leading theory, known as Diffusive Shock Acceleration (DSA), invokes Fermi acceleration off of Alfven waves at astrophysical shocks.

The pressure from the CRs can modify the shocks they are accelerated at making a highly non-linear system. Due to the computational costs of solving such a non-linear system current codes work in only one spatial dimension (1-D). 1-D systems suppress effects which are inherently multidimensional, such as instabilities and non-symmetric flows, which occur in astrophysical systems. These multidimensional effects can have a profound effect on the modeled dynamics and hence the observational characteristics of a system.

We present a modification of the AstroBEAR (Astronomical Boundary Embedded Adaptive Refinement) MHD (Magnetohydrodynamic) code, called CosmicBEAR, that allows it to treat time dependent non-linear DSA in multiple dimensions. Utilizing the power of Adaptive Mesh Refinement (AMR) in tandem with efficient methods for CR diffusion and advection allows us for the first time to explore the evolution of modified MHD shocks in more than one spatial dimension.

AAS Poster
A poster on CosmicBEAR was presented at the 214^th Meeting of the American Astronomical Society in Pasadena on June 7-11, 2009. The poster is available in PDF format below.