{
  "abstract": "We investigate how sub-sonic compressible magnetohydrodynamic (MHD) turbulence properties that are relevant for cosmic-ray (CR) transport in the Galaxy are affected by the nature and amplitude of initial fluctuations, and by the plasma compressibility $β$. We perform 3D simulations of decaying compressible ideal-MHD turbulence at $1024^3$ resolution with the PLUTO code. The level of density fluctuations in fully developed turbulence is insensitive to whether this state is reached starting from Alfvénic or fast-magnetosonic perturbations. Fast-magnetosonic injection is characterized by an early phase of rapid shock dissipation, followed by a turbulence-dominated decay with a rate comparable to that of the Alfvénic case. The contribution of fast-magnetosonic fluctuations in fully developed turbulence remains relevant only when the initial injection consists exclusively of fast modes. Large-amplitude turbulence ($δB/B_0>1$) is characterized by a nearly isotropic Kolmogorov or Iroshnikov-Kraichnan spectrum for Alfvénic or fast-magnetosonic injection, respectively. At low amplitudes ($δB/B_0\\ll1$), both initial Alfvénic and mixed-wave perturbations lead to strongly anisotropic turbulence with spectra $\\propto k_\\perp^{-5/3}$ and $\\propto k_z^{-2}$ (becoming steeper at $β\\gg1$), whereas fast-magnetosonic perturbations produce a turbulent state populated by shocks with a nearly isotropic $k^{-2}$ spectrum. Magnetic-field curvature and mirror structures are strongly sensitive to fluctuation amplitude and plasma $β$. The predicted -2.5 power-law scaling emerges only in the large-amplitude regime at high $β$. This work highlights that features of sub-sonic compressible MHD turbulence that may affect CR transport are sensitive to large-scale conditions and to the plasma $β$. Their effect on CR diffusion and field-line random walk is the object of Paper II.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.01386",
  "author_total": 5,
  "authors": [
    {
      "name": "Eleonora Puzzoni"
    },
    {
      "name": "Silvio Sergio Cerri"
    },
    {
      "name": "Dimitri Laveder"
    },
    {
      "name": "Thierry Passot"
    },
    {
      "name": "Pierre-Louis Sulem"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/f22rv6bbdr32h.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.01386",
  "fulltext_url": null,
  "id": "f22rv6bbdr32h",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.01386",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "physics.plasm-ph"
    ],
    [
      "openalex",
      "3103|Solar and Space Plasma Dynamics"
    ]
  ],
  "openalex": "W7172392230",
  "pdf_url": "https://arxiv.org/pdf/2608.01386",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/f22rv6bbdr32h.ris",
  "sources": [
    {
      "first_seen": "2026-11-03T12:20:58Z",
      "native_id": "2608.01386",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.01386"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.plasm-ph",
      "subfield": "plasma"
    }
  ],
  "title": "Sub-sonic compressible magnetohydrodynamic turbulence I. Alfvénic and fast-magnetosonic injection, amplitude dependence, and compressibility effects",
  "title_text": "Sub-sonic compressible magnetohydrodynamic turbulence I. Alfvénic and fast-magnetosonic injection, amplitude dependence, and compressibility effects",
  "type": "preprint",
  "updated_at": "2026-11-03T12:20:58Z",
  "url": "https://research.draconitic.com/paper/f22rv6bbdr32h",
  "venue": "arXiv",
  "versions": []
}