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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) ...
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, ...
The structure and stability of vortices in astrophysical discs
(University of CambridgeDepartment of Applied Mathematics and Theoretical Physics, 2015-10-06)
This thesis finds that vortex instabilities are not necessarily a barrier to their potential as
sites for planetesimal formation.
It is challenging to build planetesimals from dust within the lifetime of a protoplanetary
disc ...
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’. ...
In situ accretion of gaseous envelopes on to planetary cores embedded in evolving protoplanetary discs
(Oxford University PressMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2017-09-21)
The core accretion hypothesis posits that planets with significant gaseous envelopes accreted them from their protoplanetary discs after the formation of rocky/icy cores. Observations indicate that such exoplanets exist ...
Zonal flows in accretion discs and their role in gravito-turbulence
(University of CambridgeDepartment of Applied Mathematics and Theoretical Physics (DAMTP)St Edmund's, 2017-10-01)
This thesis focuses on the evolution of zonal flows in self-gravitating accretion discs and their resulting effect on disc stability; it also studies the process of disc gravito-turbulence, with particular emphasis given ...
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 ...
On the orbital evolution of a pair of giant planets in mean motion resonance
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-07-04)
Pairs of extrasolar giant planets in a mean motion commensurability are common with 2:1 resonance occurring most frequently. Disc–planet interaction provides a mechanism for their origin. However, the time-scale on which ...