{
  "id": "1901.02845",
  "version": "v1",
  "published": "2019-01-09T17:42:01.000Z",
  "updated": "2019-01-09T17:42:01.000Z",
  "title": "MHD simulations of the formation and propagation of protostellar jets to observational length scales",
  "authors": [
    "Jon P. Ramsey",
    "David A. Clarke"
  ],
  "comment": "26 pages, 16 figures. Accepted for publication in MNRAS",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA",
    "astro-ph.HE"
  ],
  "abstract": "We present 2.5-D global, ideal MHD simulations of magnetically and rotationally driven protostellar jets from Keplerian accretion discs, wherein only the initial magnetic field strength at the inner radius of the disc, $B_{\\rm i}$, is varied. Using the AMR-MHD code AZEUS, we self-consistently follow the jet evolution into the observational regime ($>10^3\\,\\mathrm{AU}$) with a spatial dynamic range of $\\sim6.5\\times10^5$. The simulations reveal a three-component outflow: 1) A hot, dense, super-fast and highly magnetised 'jet core'; 2) a cold, rarefied, trans-fast and highly magnetised 'sheath' surrounding the jet core and extending to a tangential discontinuity; and 3) a warm, dense, trans-slow and weakly magnetised shocked ambient medium entrained by the advancing bow shock. The simulations reveal power-law relationships between $B_{\\rm i}$ and the jet advance speed, $v_{\\rm jet}$, the average jet rotation speed, $\\langle v_\\varphi\\rangle$, as well as fluxes of mass, momentum, and kinetic energy. Quantities that do not depend on $B_{\\rm i}$ include the plasma-$\\beta$ of the transported material which, in all cases, seems to asymptote to order unity. Jets are launched by a combination of the 'magnetic tower' and 'bead-on-a-wire' mechanisms, with the former accounting for most of the jet acceleration---even for strong fields---and continuing well beyond the fast magnetosonic point. At no time does the leading bow shock leave the domain and, as such, these simulations generate large-scale jets that reproduce many of the observed properties of protostellar jets including their characteristic speeds and transported fluxes.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-01-09T17:42:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "protostellar jets",
      "observational length scales",
      "mhd simulations",
      "magnetised shocked ambient medium",
      "jet core"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 26,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}