The driving scale -- density decorrelation scale relation in a turbulent medium

Abstract

Density fluctuations produced by supersonic turbulence are of great importance to astrophysical chemical models. A property of these density fluctuations is that the two point correlation function decreases with increasing scale separation. The relation between the density decorrelation length scale ($L_{\mathrm{dec}}$) and the turbulence driving scale ($L_{\mathrm{drive}}$) determines how turbulence affects the density and chemical structures in the interstellar medium (ISM), and is a key component for using observations of atomic and molecular tracers to constrain turbulence properties. We run a set of numerical simulations of supersonic magnetohydrodynamic turbulence, with different sonic Mach numbers (${\mathcal{M}}_s=4.5,7$) , and driven on varying scales (1/2.5, 1/5, 1/7) the box length. We derive the $L_{\mathrm{dec}}-L_{\mathrm{drive}}$ relation as a function of Mach number, driving scale, and the orientation of the line-of-sight (LOS) in respect to the magnetic-field. We find that the mean ratio $L_{\mathrm{dec}}/L_{\mathrm{drive}}=0.19\pm 0.10$, when averaged over snapshots, Mach numbers, driving lengths, and the three LOSs. For LOS parallel to the magnetic field the density structures are statistically smaller and the $L_{\mathrm{dec}}-L_{\mathrm{drive}}$ relation is tighter, with $L_{\mathrm{dec}}/L_{\mathrm{drive}}=0.112\pm 0.024$. We discuss our results in the context of using observations of chemical tracers to constrain the dominant turbulence driving scale in the ISM.

arXiv commentAccepted for publication in the ApJ. Letters

References in corpus (32)

• Theory of Star Formation
• Interstellar Turbulence I: Observations and Processes
• The Neutral Atomic Phases of the ISM in the Galaxy
• Compressible Magnetohydrodynamic Turbulence: mode coupling, scaling relations, anisotropy, new regime and astrophysical implications
• The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• Tracing Magnetic Fields with Aligned Grains
• Regulation of Star Formation Rates in Multiphase Galactic Disks: a Thermal/Dynamical Equilibrium Model
• The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function
• Density Fluctuations in MHD Turbulence: Spectra, Intermittency and Topology
• Density Studies of MHD Interstellar Turbulence: Statistical Moments, Correlations and Bispectrum
• Is Turbulence in the Interstellar Medium Driven by Feedback or Gravity? An Observational Test
• Characterizing Magnetohydrodynamic Turbulence in the Small Magellanic Cloud
• Physical Properties of Giant Molecular Clouds in the Large Magellanic Cloud
• The Probability Distribution Function of Column Density in Molecular Clouds
• Superdiffusion of Cosmic Rays: Implications for Cosmic Ray Acceleration
• Velocity Spectrum for HI at High Latitudes
• Thermal Phases of the Neutral Atomic Interstellar Medium -- from Solar Metallicity to Primordial Gas
• The structure and statistics of interstellar turbulence
• Observational Diagnostics of Self-Gravitating MHD Turbulence in Giant Molecular Clouds
• Damping of MHD turbulence in partially ionized plasma: implications for cosmic ray propagation
• The HI-to-H2 Transition in a Turbulent Medium
• The Turbulence Velocity Power Spectrum of Neutral Hydrogen in the Small Magellanic Cloud
• The Lognormal Probability Distribution Function of the Perseus Molecular Cloud: A Comparison of HI and Dust
• Alfvenic Turbulence Beyond the Ambipolar Diffusion Scale
• The distribution of density in supersonic turbulence
• The Multi-phase Turbulence Density Power Spectra in the Perseus Molecular Cloud
• The Density Distribution in Turbulent Bi-stable Flows
• Chemical Abundances in a Turbulent Medium -- H${}_2$, OH${}^{+}$, H${}_2$O${}^{+}$, ArH${}^{+}$
• Developing the 3-Point Correlation Function For the Turbulent Interstellar Medium
• Probes of turbulent driving mechanisms in molecular clouds from fluctuations in synchrotron intensity
• Principal Component Analysis studies of turbulence in optically thick gas

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