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Temperature Fluctuations Driven by Magnetorotational Instability in Protoplanetary Disks

McNally, Colin P.; Hubbard, Alexander; Yang, Chao-Chin LU and Mac Low, Mordecai-Mark (2014) In Astrophysical Journal 791(1).
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
turbulence, magnetohydrodynamics (MHD), accretion disks, accretion, instabilities
in
Astrophysical Journal
volume
791
issue
1
publisher
University of Chicago Press
external identifiers
  • wos:000339657700062
  • scopus:84905186520
ISSN
0004-637X
DOI
10.1088/0004-637X/791/1/62
language
English
LU publication?
yes
id
739a0e06-a25e-48f4-884b-df716a7cea22 (old id 4665696)
date added to LUP
2014-09-25 14:39:15
date last changed
2017-06-11 04:00:32
@article{739a0e06-a25e-48f4-884b-df716a7cea22,
  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.},
  articleno    = {62},
  author       = {McNally, Colin P. and Hubbard, Alexander and Yang, Chao-Chin and Mac Low, Mordecai-Mark},
  issn         = {0004-637X},
  keyword      = {turbulence,magnetohydrodynamics (MHD),accretion disks,accretion,instabilities},
  language     = {eng},
  number       = {1},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {Temperature Fluctuations Driven by Magnetorotational Instability in Protoplanetary Disks},
  url          = {http://dx.doi.org/10.1088/0004-637X/791/1/62},
  volume       = {791},
  year         = {2014},
}