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An Isaac Newton Institute Workshop

Large-Scale Computation in Astrophysics <br> (Supported by the European Commission, Sixth Framework Programme - Marie Curie Conferences and Training Courses - MSCF-CT-2003-503674)

Staggered mesh approaches to MHD- and charged-particle simulations of astrophysical turbulence

Author: Åke Nordlund (Copenhagen University Observatory)


I will discuss the computational techniques behind recent modeling of MHD-turbulence in several astrophysical context; e.g. supersonic and super-Alfvenic turbulence in the interstellar medium and molecular clouds, subsonic MHD-turbulent in strongly stratified stellar surface layers, magnetic dissipation in the solar corona, and relativistic turbulence in collisionless shocks.

The computational techniques we have applied in all of these circumstances are related to the more conventional (Godunov-inspired) techniques in much the same way that RISC-technology relates to CISC-technology in the context of CPU-design; we attempt to minimize the number of floating point operations per meshpoint update, and hence to maximize the number of meshpoint updates per CPU per second, while still retaining a high spatial and temporal order of the updates, and the ability to capture and resolve shocks and current sheets.

I will also briefly describe the extension of these techniques to the modeling of relativistic charged particles with a particle-in-mesh (PIC) code, with which it is possible to obtain a grid resolution comparable to reasonably serious MHD-simulations; publications have already appeared based on runs with of the order of 30 million mesh points and a billion particles.

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