Large-Eddy Simulations of Magnetohydrodynamic Turbulence in Heliophysics and Astrophysics

• DOI: 10.1007/s11214-015-0190-7
• Publication Date: 2015-07-30T12:34:41Z
• Authors: Mark Miesch; William Matthaeus; Axel Brandenburg; Arakel Petrosyan; Annick Pouquet; Claude Cambon; Frank Jenko; Dmitri Uzdensky; James Stone; Steve Tobias; Juri Toomre; Marco Velli
• Keywords: Fluid Dynamics (physics.flu-dyn); FOS: Physical sciences; [SPI.MECA.MEFL] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]; Physics - Fluid Dynamics; Computational Physics (physics.comp-ph); 01 natural sciences; Physics - Plasma Physics; Space Physics (physics.space-ph); [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]; Plasma Physics (physics.plasm-ph); Astrophysics - Solar and Stellar Astrophysics; Physics - Space Physics; 13. Climate action; 0103 physical sciences; Physics - Computational Physics; Solar and Stellar Astrophysics (astro-ph.SR)

51 pages, 6 figures (Figs 2, 3, and 4 color), accepted to Space Science Reviews (in press). The paper is a product of a workshop on "LES Modeling in MHD Turbulence" held in Boulder, CO in May, 2013, sponsored by the Geophysical Turbulence Program at the National Center for Atmospheric Research<br/>We live in an age in which high-performance computing is transforming the way we do science. Previously intractable problems are now becoming accessible by means of increasingly realistic numerical simulations. One of the most enduring and most challenging of these problems is turbulence. Yet, despite these advances, the extreme parameter regimes encountered in space physics and astrophysics (as in atmospheric and oceanic physics) still preclude direct numerical simulation. Numerical models must take a Large Eddy Simulation (LES) approach, explicitly computing only a fraction of the active dynamical scales. The success of such an approach hinges on how well the model can represent the subgrid-scales (SGS) that are not explicitly resolved. In addition to the parameter regime, heliophysical and astrophysical applications must also face an equally daunting challenge: magnetism. The presence of magnetic fields in a turbulent, electrically conducting fluid flow can dramatically alter the coupling between large and small scales, with potentially profound implications for LES/SGS modeling. In this review article, we summarize the state of the art in LES modeling of turbulent magnetohydrodynamic (MHD) flows. After discussing the nature of MHD turbulence and the small-scale processes that give rise to energy dissipation, plasma heating, and magnetic reconnection, we consider how these processes may best be captured within an LES/SGS framework. We then consider several specific applications in heliophysics and astrophysics, assessing triumphs, challenges, and future directions.<br/>