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On the convective overstability in protoplanetary discs

dc.creatorLatter, Henrik Nils
dc.date.accessioned2018-11-24T23:18:43Z
dc.date.available2016-03-10T11:18:11Z
dc.date.available2018-11-24T23:18:43Z
dc.date.issued2016-01-21
dc.identifierhttps://www.repository.cam.ac.uk/handle/1810/254318
dc.identifier.urihttp://repository.aust.edu.ng/xmlui/handle/123456789/3325
dc.description.abstractThis 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 overstability’) when thermal diffusion, or cooling, is neither too strong nor too weak. I revisit the linear theory of the instability, discuss its prevalence in protoplanetary discs, and show that unstable modes are exact non-linear solutions in the local Boussinesq limit. Overstable modes cannot grow indefinitely, however, as they are subject to a secondary parametric instability that limits their amplitudes to relatively low levels. If parasites set the saturation level of the ensuing turbulence then the convective overstability is probably too weak to drive significant angular momentum transport or to generate vortices. But I also discuss an alternative, and far more vigorous, saturation route that generates radial ‘layers’ or ‘zonal flows’ (witnessed in semiconvection). Numerical simulations are required to determine which outcome is favoured in realistic discs, and consequently how important the instability is for disc dynamics.
dc.languageen
dc.publisherOxford University Press
dc.publisherMonthly Notices of the Royal Astronomical Society
dc.subjectconvection
dc.subjectinstabilities
dc.subjectturbulence
dc.subjectwaves
dc.subjectprotoplanetary discs
dc.titleOn the convective overstability in protoplanetary discs
dc.typeArticle


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