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On dust–gas gravitational instabilities in protoplanetary discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2017-01-11)
In protoplanetary discs the aerodynamical friction between particles and gas induces a variety of instabilities that facilitate planet formation. Of these we examine the so-called ‘secular gravitational instability’ (SGI) ...
Local models of astrophysical discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2017-12-01)
Local models of gaseous accretion discs have been successfully employed for decades to describe an assortment of small-scale phenomena, from instabilities and turbulence, to dust dynamics and planet formation. For the most ...
Vortices and the saturation of the vertical shear instability in protoplanetary discs
(Monthly Notices of the Royal Astronomical Society, 2018-03-01)
Spiral density waves and vertical circulation in protoplanetary discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2018-06-01)
Spiral density waves dominate several facets of accretion disc dynamics – planet-disc interactions and gravitational instability (GI) most prominently. Though they have been examined thoroughly in two-dimensional simulations, ...
On the survival of zombie vortices in protoplanetary discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-09-06)
Recently it has been proposed that the zombie vortex instability (ZVI) could precipitate hydrodynamical activity and angular momentum transport in unmagnetized regions of protoplanetary discs, also known as ‘dead zones’. ...
The stress–pressure relationship in simulations of MRI-induced turbulence
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-01-01)
We determine how MRI (magnetorotational instability)-turbulent stresses depend on gas pressure via a suite of unstratified shearing box simulations. Earlier numerical work reported only a very weak dependence at best, ...
On the convective overstability in protoplanetary discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-01-21)
This paper explores the driving of low-level hydrodynamical activity in protoplanetary-disc dead zones. A small adverse radial entropy gradient, ordinarily stabilized by rotation, excites oscillatory convection (‘convective ...
Gravitoturbulence in magnetized protostellar discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-05-11)
Gravitational instability (GI) features in several aspects of protostellar disc evolution, most notably in angular momentum transport, fragmentation, and the outbursts exemplified by FU Ori and EX Lupi systems. The outer ...
MRI turbulence and thermal instability in accretion discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2017-06)
A long-standing puzzle in the study of black hole accretion concerns the presence or not of thermal instability. Classical theory predicts that the encircling accretion disc is unstable, as do some self-consistent ...