The sonic scale of interstellar turbulence

2020/11/12 by Christoph Federrath, Ralf S. Klessen, Luigi Iapichino +1
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Cascade #Chemistry #Galaxy #Interstellar medium #Mach number #Mechanics #Molecular cloud #Physics #Scale (ratio) #Star formation #Stars #Stellar, planetary, and galactic studies #Supersonic speed #Turbulence #astro-ph.GA #astro-ph.SR #physics.comp-ph #physics.flu-dyn

paper · pdf · doi:10.1038/s41550-020-01282-z

22 pages, 9 figures, Nat Astron (2021)

arxiv created 2020/11/12 · openalex publication_date 2021/01/11 · arxiv updated 2021/01/15 · openalex created_date 2021/01/18 · openalex updated_date 2026/08/01

Abstract

Understanding the physics of turbulence is crucial for many applications, including weather, industry, and astrophysics. In the interstellar medium (ISM), supersonic turbulence plays a crucial role in controlling the gas density and velocity structure, and ultimately the birth of stars. Here we present a simulation of interstellar turbulence with a grid resolution of 10048³ cells that allows us to determine the position and width of the sonic scale (l_s) - the transition from supersonic to subsonic turbulence. The simulation simultaneously resolves the supersonic and subsonic cascade, v(l) ~ l^p, where we measure p_sup = 0.49 +/- 0.01 and p_sub = 0.39 +/- 0.02, respectively. We find that l_s agrees with the relation l_s / L = phi_s Mach^(-1/p_sup), where Mach is the three-dimensional Mach number, and L is either the driving scale of turbulence or the diameter of a molecular cloud. If L is the driving scale, we measure phi_s = 0.42 (+0.12) (-0.09), primarily because of the separation between the driving scale and the start of the supersonic cascade. For a supersonic cascade extending beyond the cloud scale, we get phi_s = 0.91 (+0.25) (-0.20). In both cases, phi_s < 1, because we find that the supersonic cascade transitions smoothly to the subsonic cascade over a factor of 3 in scale, instead of a sharp transition. Our measurements provide quantitative input for turbulence-regulated models of filament structure and star formation in molecular clouds.

Citations

• Molecular Cloud Evolution
• A Holistic Scenario of Turbulent Molecular Cloud Evolution and Control of the Star Formation Efficiency: First Tests
• FLASH: An Adaptive Mesh Hydrodynamics Code for Modeling Astrophysical Thermonuclear Flashes
• The interstellar environment of our galaxy
• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from theHerschelGould Belt Survey
• Turbulent molecular clouds
• The Universality of Turbulence in Galactic Molecular Clouds
• Mach Number Dependence of Turbulent Magnetic Field Amplification: Solenoidal versus Compressive Flows
• Mach number dependence of the onset of dynamo action
• Theory of Star Formation
• The Fractal Dimension of Projected Clouds
• A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and tests
• On the shape and completeness of the column density probability distribution function of molecular clouds
• On the structure of the turbulent interstellar clouds . Influence of the equation of state on the dynamics of 3D compressible flows

Cited by

• Local relaxation and scale-dependent alignment in compressible, magnetized turbulence