Temperature fluctuations driven by magnetorotational instability in protoplanetary disks

Journal Article · Sun Aug 10 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/791/1/62· OSTI ID:22365350

McNally, Colin P. ^[1]; Hubbard, Alexander; Low, Mordecai-Mark Mac ^[2]; Yang, Chao-Chin ^[3]

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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)

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.

• OSTI ID: 22365350
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 791; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
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