The role of the sonic scale in the growth of magnetic field in compressible turbulence
| Autor: | Michael Mond, Itzhak Fouxon |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Physics
Field (physics) Scale (ratio) Turbulence Fluid Dynamics (physics.flu-dyn) FOS: Physical sciences Astronomy and Astrophysics Physics - Fluid Dynamics Mechanics 01 natural sciences Physics::Fluid Dynamics symbols.namesake Astrophysics - Solar and Stellar Astrophysics Mach number Space and Planetary Science Incompressible flow Physics::Space Physics 0103 physical sciences symbols Supersonic speed Magnetohydrodynamics 010306 general physics 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Dynamo |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 493:4400-4408 |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/staa582 |
| Popis: | We study the growth of small fluctuations of magnetic field in supersonic turbulence, the small-scale dynamo. The growth is due to the fastest turbulent eddies above the resistive scale. We observe that for supersonic turbulence these eddies are effectively incompressible which creates a robust structure of the growth. The eddies are localised below the sonic scale $l_s$ defined as the scale where the typical velocity of the turbulent eddies equals the speed of sound. Thus the flow below $l_s$ is effectively incompressible and the field growth proceeds as in incompressible flow. At large Mach numbers $l_s$ is much smaller than the integral scale of turbulence so the fastest growing mode of the magnetic field belongs to small-scale turbulence. We derive this mode and the associated growth rate numerically in a white noise in time model of turbulence. The relevance of this model relies on considering evolution time larger than the correlation time of turbulence. Comment: 5 pages, 2 figures |
| Databáze: | OpenAIRE |
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