Global 3D radiation magnetohydrodynamic simulations for FU Ori's accretion disc and observational signatures of magnetic fields

Zhaohuan Zhu, Yan Fei Jiang, James M. Stone

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

FU Ori is the prototype of FU Orionis systems that are outbursting protoplanetary discs. Magnetic fields in FU Ori's accretion discs have previously been detected using spectropolarimetry observations for Zeeman effects. We carry out global radiation ideal MHD simulations to study FU Ori's inner accretion disc. We find that (1) when the disc is threaded by vertical magnetic fields, most accretion occurs in the magnetically dominated atmosphere at z ∼R, similar to the 'surface accretion' mechanism in previous locally isothermal MHD simulations. (2) A moderate disc wind is launched in the vertical field simulations with a terminal speed of ∼300-500 km s-1 and a mass-loss rate of 1-10 per cent the disc accretion rate, which is consistent with observations. Disc wind fails to be launched in simulations with net toroidal magnetic fields. (3) The disc photosphere at the unit optical depth can be either in the wind launching region or the accreting surface region. Magnetic fields have drastically different directions and magnitudes between these two regions. Our fiducial model agrees with previous optical Zeeman observations regarding both the field directions and magnitudes. On the other hand, simulations indicate that future Zeeman observations at near-IR wavelengths or towards other FU Orionis systems may reveal very different magnetic field structures. (4) Due to energy loss by the disc wind, the disc photosphere temperature is lower than that predicted by the thin disc theory, and the previously inferred disc accretion rate may be lower than the real accretion rate by a factor of ∼2-3.

Original languageEnglish (US)
Pages (from-to)3494-3514
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume495
Issue number3
DOIs
StatePublished - May 14 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • MHD
  • accretion, accretion discs
  • astroparticle physics
  • dynamo
  • instabilities
  • turbulence

Fingerprint

Dive into the research topics of 'Global 3D radiation magnetohydrodynamic simulations for FU Ori's accretion disc and observational signatures of magnetic fields'. Together they form a unique fingerprint.

Cite this