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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) ...
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’. ...
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 ...