The spectrum of magnetized turbulence in the interstellar medium

2025/04/07 by James R. Beattie, Christoph Federrath, Ralf S. Klessen +3 · 3 voices · 14 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Computational physics #Galaxy #Interstellar medium #Mechanics #Physics #Quantum mechanics #Solar and Space Plasma Dynamics #Spectrum (functional analysis) #Stellar, planetary, and galactic studies #Turbulence

paper · pdf · doi:10.1038/s41550-025-02551-5

published in Nature Astronomy 9(8), 1195-1205 (Nature Portfolio)

openalex publication_date 2025/05/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

The interstellar medium (ISM) of our Galaxy is magnetized, compressible and turbulent, influencing many key ISM properties, like star formation, cosmic ray transport, and metal and phase mixing. Yet, basic statistics describing compressible, magnetized turbulence remain uncertain. Utilizing grid resolutions up to 10,080³ cells, we simulate highly-compressible, magnetized ISM-style turbulence with a magnetic field maintained by a small-scale dynamo. We measure two coexisting kinetic energy cascades, E_{\rm kin}(k) ∝ k^-n, in the turbulence, separating the plasma into scales that are non-locally interacting, supersonic and weakly magnetized (n=2.01± 0.03≈ 2) and locally interacting, subsonic and highly magnetized (n=1.465± 0.002≈ 3/2), where k is the wavenumber. We show that the 3/2 spectrum can be explained with scale-dependent kinetic energy fluxes and velocity-magnetic field alignment. On the highly magnetized modes, the magnetic energy spectrum forms a local cascade (n=1.798± 0.001≈ 9/5), deviating from any known ab initio theory. With a new generation of radio telescopes coming online, these results provide a means to directly test if the ISM in our Galaxy is maintained by the compressible turbulent motions from within it.

Citations

• Inertial-Range Spectrum of Hydromagnetic Turbulence
• Theory of Star Formation
• Magnetic field amplification in turbulent astrophysical plasmas
• MHD turbulence: a biased review
• Prototype Faraday Rotation Measure Catalogs from the Polarisation Sky Survey of the Universe’s Magnetism (POSSUM) Pilot Observations
• FLASH: An Adaptive Mesh Hydrodynamics Code for Modeling Astrophysical Thermonuclear Flashes

Cited by

• Compressible Navier-Stokes Flow in Schrödinger-Type Variables
• The universal growth of magnetic energy during the nonlinear phase of subsonic and supersonic small-scale dynamos
• Supernovae drive large-scale, incompressible turbulence through small-scale instabilities
• Cascading from the winds to the disk: the universality of supernovae-driven turbulence in different galactic interstellar media
• Cosmic ray and plasma coupling for isothermal supersonic turbulence in the magnetized interstellar medium
• Universal relations between parallel and perpendicular spectral power law exponents in non-axisymmetric magnetohydrodynamic turbulence
• Local relaxation and scale-dependent alignment in compressible, magnetized turbulence

Discussions

• Here's another sample from the largest-ever computer simulation of magnetic turbulence in a galaxy. Knowledge is powerful. It's also beautiful. Let's protect it & keep pursuing it. Full paper at link. [bsky, 19 points, 1 comments]
• The spectrum of magnetized turbulence in the interstellar medium: arxiv.org/abs/2504.07136 -> Astrophysicists explore our galaxy’s magnetic turbulence in unprecedented detail using a new computer mode [bsky, 0 points, 0 comments]
• arxiv.org/abs/2504.07136 [bsky, 0 points, 0 comments]

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