{
  "id": "1212.0136",
  "version": "v1",
  "published": "2012-12-01T17:08:12.000Z",
  "updated": "2012-12-01T17:08:12.000Z",
  "title": "What controls the magnetic geometry of M dwarfs?",
  "authors": [
    "T. Gastine",
    "J. Morin",
    "L. Duarte",
    "A. Reiners",
    "U. R. Christensen",
    "J. Wicht"
  ],
  "comment": "4 pages, 4 figures, accepted for publication in A&A",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Context: observations of rapidly rotating M dwarfs show a broad variety of large-scale magnetic fields encompassing dipole-dominated and multipolar geometries. In dynamo models, the relative importance of inertia in the force balance -- quantified by the local Rossby number -- is known to have a strong impact on the magnetic field geometry. Aims: we aim to assess the relevance of the local Rossby number in controlling the large-scale magnetic field geometry of M dwarfs. Methods: we explore the similarities between anelastic dynamo models in spherical shells and observations of active M-dwarfs, focusing on field geometries derived from spectropolarimetric studies. To do so, we construct observation-based quantities aimed to reflect the diagnostic parameters employed in numerical models. Results: the transition between dipole-dominated and multipolar large-scale fields in early to mid M dwarfs is tentatively attributed to a Rossby number threshold. We interpret late M dwarfs magnetism to result from a dynamo bistability occurring at low Rossby number. By analogy with numerical models, we expect different amplitudes of differential rotation on the two dynamo branches.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-12-01T17:08:12.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "magnetic geometry",
      "local rossby number",
      "magnetic fields encompassing",
      "large-scale magnetic field geometry",
      "dynamo models"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1051/0004-6361/201220317",
      "journal": "Astronomy and Astrophysics",
      "year": 2013,
      "month": "Jan",
      "volume": 549
    },
    "note": {
      "typesetting": "TeX",
      "pages": 4,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1205066,
      "adsabs": "2013A&A...549L...5G"
    }
  }
}