Compressible turbulence in the interstellar medium: New insights from a high-resolution supersonic turbulence simulation

Abstract

The role of supersonic turbulence in structuring the interstellar medium (ISM) remains an unsettled question. Here, this problem is investigated using a newexact law of compressible isothermal hydrodynamic turbulence, which involves two-point correlations in physical space. The new law is shown to have a compact expression that contains a single flux term reminiscent of the incompressible case and a source term with a simple expression whose sign is given by the divergence of the velocity. The law is then used to investigate the properties of such a turbulence at integral Mach number $4$ produced by a massive numerical simulation with a grid resolution of $10,048^3$ points. The flux (resp. source) term was found to have positive (resp. negative) contribution to the total energy cascade rate, which is interpreted as a direct cascade amplified by compression, while their sum is constant in the inertial range. Using a local (in space) analysis it is shown that the source is mainly driven by filamentary structures in which the flux is negligible. Taking positive defined correlations reveals the existence of different turbulent regimes separated by the sonic scale, which determines the scale over which the non-negligible source modifies the scaling of the flux. Our study provides new insight into the dynamics and structures of supersonic interstellar turbulence.

8 pages, 6 Figures

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Cited by in corpus (8)

• General exact law of compressible isentropic magnetohydrodynamic flows: theory and spacecraft observations in the solar wind
• The spectrum of magnetized turbulence in the interstellar medium
• Scale dependence and cross-scale transfer of kinetic energy in compressible hydrodynamic turbulence at moderate Reynolds numbers
• An in-depth numerical study of exact laws for compressible Hall magnetohydrodynamic turbulence
• Energy transfer, discontinuities and heating in the inner solar wind measured with a weak and local formulation of the Politano-Pouquet law
• Proof of the zeroth law of turbulence in one-dimensional compressible magnetohydrodynamics and shock heating
• Structure of iso-density sets in supersonic isothermal turbulence
• Diagnosing Turbulence in the Neutral and Molecular Interstellar Medium of Galaxies