scholarly journals Toward Consistent Models of Protoplanetary Discs

2004 ◽  
Vol 202 ◽  
pp. 359-361
Author(s):  
Mauricio Reyes-Ruiz
Keyword(s):  
Dead Zone ◽  
Linear Analysis ◽  
Vertical Stratification ◽  
Magnetorotational Instability ◽  
Vertical Diffusivity ◽  
Magnetic Diffusivity ◽  
Protoplanetary Discs

In this paper we present results on the effect of the vertical stratification of magnetic diffusivity, expected in current models of protoplanetary discs, on the development of the magnetorotational instability. Specifically, on the basis of a quasi-global, linear analysis we study the operation of the magnetorotational instability across the so-called dead zone of protoplanetary discs. Our results indicate that the predicted strong vertical diffusivity gradients can damp the instability in such regions. This suggests the necessity of a revision of current models for the structure and evolution of protoplanetary discs.

scholarly journals On the vortex evolution in non-isothermal protoplanetary discs

2020 ◽  
Vol 493 (2) ◽  
pp. 3014-3025
Author(s):  
D Tarczay-Nehéz ◽  
Zs Regály ◽  
E Vorobyov
Keyword(s):  
Large Scale ◽  
Planet Formation ◽  
Dead Zone ◽  
Giant Planet ◽  
Building Blocks ◽  
Outer Edge ◽  
Wave Instability ◽  
Large Scale Vortex ◽  
Self Gravity ◽  
Protoplanetary Discs

ABSTRACT It is believed that large-scale horseshoe-like brightness asymmetries found in dozens of transitional protoplanetary discs are caused by anticyclonic vortices. These vortices can play a key role in planet formation, as mm-sized dust – the building blocks of planets – can be accumulated inside them. Anticyclonic vortices are formed by the Rossby wave instability, which can be excited at the gap edges opened by a giant planet or at sharp viscosity transitions of accretionally inactive regions. It is known that vortices are prone to stretching and subsequent dissolution due to disc self-gravity for canonical disc masses in the isothermal approximation. To improve the hydrodynamic model of protoplanetary discs, we include the disc thermodynamics in our model. In this paper, we present our results on the evolution of the vortices formed at the outer edge of an accretionally inactive region (dead zone) assuming an ideal equation of state and taking PdV work, disc cooling in the β-approximation, and disc self-gravity into account. Thermodynamics affects the offset and the mode number (referring to the number of small vortices at the early phase) of the RWI excitation, as well as the strength, shape, and lifetime of the large-scale vortex formed through merging of the initial small vortices. We found that the inclusion of gas thermodynamics results in stronger, however decreased lifetime vortices. Our results suggest that a hypothetical vortex-aided planet formation scenario favours effectively cooling discs.

scholarly journals High-resolution simulations of planetesimal formation in turbulent protoplanetary discs

2010 ◽  
Vol 6 (S276) ◽  
pp. 89-94
Author(s):  
Anders Johansen ◽  
Hubert Klahr ◽  
Thomas Henning
Keyword(s):  
High Resolution ◽  
Computer Simulations ◽  
Large Scale ◽  
Dynamical Friction ◽  
Magnetorotational Instability ◽  
Dust Dynamics ◽  
Protoplanetary Discs

AbstractWe present high resolution computer simulations of dust dynamics and planetesimal formation in turbulence triggered by the magnetorotational instability. Particles representing approximately meter-sized boulders clump in large scale overpressure regions in the simulation box. These overdensities readily contract due to the combined gravity of the particles to form gravitationally bound clusters with masses ranging from a few to several ten times the mass of the dwarf planet Ceres. Gravitationally bound clumps are observed to collide and merge at both moderate and high resolution. The collisional products form the top end of a distribution of planetesimal masses ranging from less than one Ceres mass to 35 Ceres masses. It remains uncertain whether collisions are driven by dynamical friction or underresolution of clumps.

scholarly journals Dead zone formation and non-steady hyperaccretion in collapsar disks

2008 ◽  
Vol 4 (S259) ◽  
pp. 119-120
Author(s):  
Youhei Masada
Keyword(s):  
Gamma Ray ◽  
Dead Zone ◽  
Mhd Turbulence ◽  
Magnetorotational Instability ◽  
Zone Formation ◽  
Central Engine ◽  
Accretion Model ◽  
Viscous Media ◽  
Energy And Momentum ◽  
Inner Region

AbstractIn ultra dense and hot region realized in stellar core-collapse, neutrino takes major role in energy and momentum transports. We investigate the growth of magnetorotational instability (MRI) in neutrino viscous matter by using linear theory. It is found from the local linear analysis that the neutrino viscosity can suppress the MRI in the regime of weak magnetic field (B ≪ 1014G). This suggest that MHD turbulence sustained by the MRI might not be driven efficiently in the neutrino viscous media. Applying this result to collapsar disk, which is known as the central engine of gamma-ray burst (GRB), we find that the MRI can be suppressed only in its inner region. Based on this finding, a new evolutionary scenario of collapsar disk, “Episodic Disk Accretion Model” are proposed.

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