Work

Tearing Instability in Gyrotropic Magnetohydrodynamics: Effects of Equilibrium Pressure Anisotropy

Year: 2026

Type: article

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

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/aea20b

Authors: Grzegorz Kowal, Gabriel L. Ferreira-Santos, Diego A. Falceta-Gonçalves

Institutions: Universidade de São Paulo, Instituto Nacional de Pesquisas Espaciais

Language: English

Topic: Solar and Space Plasma Dynamics

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

Funder: Fundação de Amparo à Pesquisa do Estado de São Paulo