{
  "abstract": "Weakly collisional plasmas are widespread in astrophysics and can sustain pressure anisotropy, yet most analytical tearing-mode scalings assume an isotropic equilibrium. We develop a linear theory of resistive tearing in nonideal gyrotropic MHD for a force-free Harris current sheet characterized by perpendicular plasma- β β ₀ and parallel-minus-perpendicular beta difference Δ β ₀ . In the ideal outer region, anisotropy changes the far-field decay rate and the matching parameter Δ ′ and sets the upper wavenumber cutoff for the localized tearing instability, α ≡ k a < α c = A / R 0 , where A = 1 − Δ β 0 / 2 , R 0 = 1 + 1 2 [ ( γ ∥ + γ ⊥ − 2 ) β 0 + γ ∥ Δ β 0 ] , and γ ∥ and γ ⊥ are the parallel and perpendicular polytropic indices specifying the gyrotropic pressure closure. In the resistive inner layer, anisotropy enters the leading momentum balance through A . We derive low- and high-wavenumber asymptotic branches. By matching them at their crossover, we identify the fastest-growing mode and find the maximum growth rate scaling γ max τ A ∼ A 1 / 2 R 0 − 1 / 4 S − 1 / 2 , where S is the Lundquist number and τ A is the Alfvén crossing time. Thus, the classical Lundquist-number exponent is retained, while the prefactor depends on the equilibrium anisotropy, plasma- β , and gyrotropic closure. The numerical eigenvalues support the low-wavenumber branch and are consistent with the high-wavenumber branch when Δ ′ is obtained by direct numerical integration of the ideal outer equation. Within the localized-mode and pressure-positive domain, positive Δ β ₀ generally suppresses tearing and broadens the inner layer, whereas negative Δ β ₀ enhances growth and shifts the fastest mode to a larger wavenumber. By identifying how prescribed equilibrium pressure anisotropy modifies both ideal outer matching and resistive inner-layer dynamics, this work provides a controlled extension of classical tearing theory within the gyrotropic MHD regime.",
  "abstract_shown": true,
  "affiliations": [
    "University of São Paulo",
    "National Institute for Space Research"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Grzegorz Kowal",
      "orcid": "0000-0002-0176-9909"
    },
    {
      "affs": [
        1
      ],
      "name": "Gabriel L. Ferreira-Santos",
      "orcid": "0000-0001-7144-5777"
    },
    {
      "affs": [
        0
      ],
      "name": "Diego A. Falceta-Gonçalves",
      "orcid": "0000-0002-1914-6654"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/77h9s7ecedd8r.bib",
  "cited_by": 0,
  "doi": "10.3847/1538-4357/aea20b",
  "fulltext_url": null,
  "id": "77h9s7ecedd8r",
  "issns": [
    "0004-637X",
    "1538-4357"
  ],
  "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea20b",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3103|Solar and Space Plasma Dynamics"
    ]
  ],
  "openalex": "W7221727971",
  "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea20b/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-13",
  "publisher": "American Astronomical Society",
  "ris": "https://research.draconitic.com/paper/77h9s7ecedd8r.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:11Z",
      "native_id": "10.3847/1538-4357/aea20b",
      "source": "crossref",
      "url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea20b"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Solar and Space Plasma Dynamics",
      "subfield": "stellar"
    }
  ],
  "title": "Tearing Instability in Gyrotropic Magnetohydrodynamics: Effects of Equilibrium Pressure Anisotropy",
  "title_text": "Tearing Instability in Gyrotropic Magnetohydrodynamics: Effects of Equilibrium Pressure Anisotropy",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:11Z",
  "url": "https://research.draconitic.com/paper/77h9s7ecedd8r",
  "venue": "The Astrophysical Journal",
  "versions": []
}