2014/11/30 by Christoph Federrath, Jennifer Schober, Stefano Bovino +1 · 5 citations
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Dynamo #Dynamo theory #Geomagnetism and Paleomagnetism Studies #Ionosphere and magnetosphere dynamics #Magnetic Reynolds number #Magnetic field #Magnetohydrodynamics #Solar and Space Plasma Dynamics #Solar dynamo #Supersonic speed #Turbulence #astro-ph.CO #astro-ph.GA #astro-ph.SR #physics.comp-ph #physics.flu-dyn
paper · pdf · doi:10.1088/2041-8205/797/2/l19
published as The Astrophysical Journal Letters (2014), Volume 797, L19 · 6 pages, 3 figures, The Astrophysical Journal Letters (in press), Simulation movies at http://www.mso.anu.edu.au/~chfeder/pubs/dynamo_pm/dynamo_pm.html
arxiv created 2014/12/01 · openalex publication_date 2014/12/03 · arxiv updated 2014/12/05 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The turbulent dynamo may explain the origin of cosmic magnetism. While the exponential amplification of magnetic fields has been studied for incompressible gases, little is known about dynamo action in highly compressible, supersonic plasmas, such as the interstellar medium of galaxies and the early universe. Here we perform the first quantitative comparison of theoretical models of the dynamo growth rate and saturation level with three-dimensional magnetohydrodynamical simulations of supersonic turbulence with grid resolutions of up to 1024 3 cells. We obtain numerical convergence and find that dynamo action occurs for both low and high magnetic Prandtl numbers Pm = ν/η = 0.1–10 (the ratio of viscous to magnetic dissipation), which had so far only been seen for Pm ⩾ 1 in supersonic turbulence. We measure the critical magnetic Reynolds number, , showing that the compressible dynamo is almost as efficient as in incompressible gas. Considering the physical conditions of the present and early universe, we conclude that magnetic fields need to be taken into account during structure formation from the early to the present cosmic ages, because they suppress gas fragmentation and drive powerful jets and outflows, both greatly affecting the initial mass function of stars.