{
  "id": "2007.15967",
  "version": "v1",
  "published": "2020-07-31T11:13:25.000Z",
  "updated": "2020-07-31T11:13:25.000Z",
  "title": "Magnetohydrodynamics of protoplanetary discs",
  "authors": [
    "G. Lesur"
  ],
  "comment": "115 pages, 46 figures, accepted for publication in the lecture notes series of the Journal of Plasma Physics (Cambridge University Press)",
  "categories": [
    "astro-ph.SR",
    "astro-ph.EP",
    "astro-ph.HE",
    "physics.flu-dyn",
    "physics.plasm-ph"
  ],
  "abstract": "Protoplanetary discs are made of gas and dust orbiting a young star. They are also the birth place of planetary systems, which motivates a large amount of observational and theoretical research. In these lecture notes, I present a review of the magnetic mechanisms applied to the outer regions R>1 AU of these discs, which are the planet-formation regions. In contrast to usual astrophysical plasmas, the gas in these regions is noticeably cold (T<300 K) and dense, which implies a very low ionisation fraction close to the disc midplane. In these notes, I deliberately ignore the innermost R~0.1 AU region which is influenced by the star-disk interaction and various radiative effects. I start by presenting a short overview of the observational evidence for the dynamics of these objects. I then introduce the methods and approximations used to model these plasmas, including non-ideal MHD, and the uncertainties associated with this approach. In this framework, I explain how the global dynamics of these discs is modelled, and I present a stability analysis of this plasma in the local approximation, introducing the non-ideal magneto-rotational instability. Following this mostly analytical part, I discuss numerical models which have been used to describe the saturation mechanisms of this instability, and the formation of large-scale structures by various saturation mechanisms. Finally, I show that local numerical models are insufficient since magnetised winds are also emitted from the surface of these objects. After a short introduction on winds physics, I present global models of protoplanetary discs, including both a large-scale wind and the non-ideal dynamics of the disc.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-07-31T11:13:25.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "protoplanetary discs",
      "saturation mechanisms",
      "magnetohydrodynamics",
      "low ionisation fraction close",
      "non-ideal magneto-rotational instability"
    ],
    "tags": [
      "lecture notes"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 115,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}