Temperature Fluctuations Driven by Magnetorotational Instability in Protoplanetary Disks

Research output: Contribution to journalArticle

Abstract

The magnetorotational instability (MRI) drives magnetized turbulence in sufficiently ionized regions of protoplanetary disks, leading to mass accretion. The dissipation of the potential energy associated with this accretion determines the thermal structure of accreting regions. Until recently, the heating from the turbulence has only been treated in an azimuthally averaged sense, neglecting local fluctuations. However, magnetized turbulence dissipates its energy intermittently in current sheet structures. We study this intermittent energy dissipation using high resolution numerical models including a treatment of radiative thermal diffusion in an optically thick regime. Our models predict that these turbulent current sheets drive order-unity temperature variations even where the MRI is damped strongly by Ohmic resistivity. This implies that the current sheet structures where energy dissipation occurs must be well-resolved to correctly capture the flow structure in numerical models. Higher resolutions are required to resolve energy dissipation than to resolve the magnetic field strength or accretion stresses. The temperature variations are large enough to have major consequences for mineral formation in disks, including melting chondrules, remelting calcium-aluminum-rich inclusions, and annealing silicates; and may drive hysteresis: current sheets in MRI active regions could be significantly more conductive than the remainder of the disk.

Details

Authors
  • Colin P. McNally
  • Alexander Hubbard
  • Chao-Chin Yang
  • Mordecai-Mark Mac Low
Organisations
External organisations
  • American Museum of Natural History
  • Niels Bohr Institute
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • turbulence, magnetohydrodynamics (MHD), accretion disks, accretion, instabilities
Original languageEnglish
Article number62
JournalAstrophysical Journal
Volume791
Issue number1
Publication statusPublished - 2014
Publication categoryResearch
Peer-reviewedYes