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Title: Temperature fluctuations driven by magnetorotational instability in protoplanetary disks

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.

Authors:
 [1]; ;  [2];  [3]
  1. Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø (Denmark)
  2. Department of Astrophysics, American Museum of Natural History, New York, NY 10024-5192 (United States)
  3. Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, SE-22100 Lund (Sweden)
Publication Date:
OSTI Identifier:
22365350
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ALUMINIUM; ANNEALING; CALCIUM; CAPTURE; ENERGY LOSSES; FLUCTUATIONS; HYSTERESIS; INCLUSIONS; INSTABILITY; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MASS; MINERALS; NMR IMAGING; PROTOPLANETS; RESOLUTION; SILICATES; THERMAL DIFFUSION; TURBULENCE

Citation Formats

McNally, Colin P., Hubbard, Alexander, Low, Mordecai-Mark Mac, and Yang, Chao-Chin, E-mail: cmcnally@nbi.dk, E-mail: ahubbard@amnh.org, E-mail: mordecai@amnh.org, E-mail: ccyang@astro.lu.se. Temperature fluctuations driven by magnetorotational instability in protoplanetary disks. United States: N. p., 2014. Web. doi:10.1088/0004-637X/791/1/62.
McNally, Colin P., Hubbard, Alexander, Low, Mordecai-Mark Mac, & Yang, Chao-Chin, E-mail: cmcnally@nbi.dk, E-mail: ahubbard@amnh.org, E-mail: mordecai@amnh.org, E-mail: ccyang@astro.lu.se. Temperature fluctuations driven by magnetorotational instability in protoplanetary disks. United States. doi:10.1088/0004-637X/791/1/62.
McNally, Colin P., Hubbard, Alexander, Low, Mordecai-Mark Mac, and Yang, Chao-Chin, E-mail: cmcnally@nbi.dk, E-mail: ahubbard@amnh.org, E-mail: mordecai@amnh.org, E-mail: ccyang@astro.lu.se. Sun . "Temperature fluctuations driven by magnetorotational instability in protoplanetary disks". United States. doi:10.1088/0004-637X/791/1/62.
@article{osti_22365350,
title = {Temperature fluctuations driven by magnetorotational instability in protoplanetary disks},
author = {McNally, Colin P. and Hubbard, Alexander and Low, Mordecai-Mark Mac and Yang, Chao-Chin, E-mail: cmcnally@nbi.dk, E-mail: ahubbard@amnh.org, E-mail: mordecai@amnh.org, E-mail: ccyang@astro.lu.se},
abstractNote = {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.},
doi = {10.1088/0004-637X/791/1/62},
journal = {Astrophysical Journal},
number = 1,
volume = 791,
place = {United States},
year = {Sun Aug 10 00:00:00 EDT 2014},
month = {Sun Aug 10 00:00:00 EDT 2014}
}