{
  "abstract": "Athena++ is a finite-volume astrophysical magnetohydrodynamics (MHD) code. As of writing, isotropic thermal conduction and kinematic viscosity, Ohmic resistivity, and ambipolar diffusion are present in the main branch. Here we present a fork of Athena++, ``Athena-Aniso''. It implements fully anisotropic thermal conduction (parallel, perpendicular, and the Righi--Leduc effect); anisotropic viscosity (all five Braginskii viscosity tensors); the Hall effect; and several thermoelectric effects (Peltier, Seebeck, Nernst, and Ettingshausen). These effects can be weighted by ionisation fraction in a partially ionised gas, with the neutral part diffusing isotropically. We have also added isotropic bulk viscosity. The Biermann battery is not implemented here. The dissipative terms have super-time-stepping support, while the non-dissipative terms are combined with the ideal MHD flux. A CFL condition for all terms is derived and implemented using von Neumann stability analysis. The dissipative terms are found to be stable under first-order time integration. The non-dissipative terms are found to be stable under third-order time integration. We additionally derive new signal speeds for a modified HLLE Riemann solver. These suppress grid-scale non-linear instabilities still present in the non-dissipative terms. The Nernst/Ettingshausen system is found to be ill-posed unless it is stabilised by both perpendicular thermal conduction and perpendicular magnetic diffusion. We derive a well-posedness criterion for this. We provide numerical tests of each implemented effect against derived analytical solutions.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.05086",
  "author_total": 2,
  "authors": [
    {
      "name": "Alexandra F. Albery"
    },
    {
      "name": "Julian M. Pittard"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/e3wak5a0zbj7t.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.05086",
  "fulltext_url": null,
  "id": "e3wak5a0zbj7t",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.05086",
  "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.IM"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.05086",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/e3wak5a0zbj7t.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T15:21:25Z",
      "native_id": "2611.05086",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.05086"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    }
  ],
  "title": "von Neumann Stability Analysis of Braginskii MHD Thermal Conduction, Viscosity, Magnetic Diffusion, and Thermoelectric Effects and an Implementation in Athena++",
  "title_text": "von Neumann Stability Analysis of Braginskii MHD Thermal Conduction, Viscosity, Magnetic Diffusion, and Thermoelectric Effects and an Implementation in Athena++",
  "type": "preprint",
  "updated_at": "2026-11-09T00:20:39Z",
  "url": "https://research.draconitic.com/paper/e3wak5a0zbj7t",
  "venue": "arXiv",
  "versions": []
}