Abstract
ABSTRACT Protoplanetary discs at certain radii exhibit adverse radial entropy gradients that can drive oscillatory convection (‘convective overstability’; COS). The ensuing hydrodynamical activity may reshape the radial thermal structure of the disc while mixing solid material radially and vertically or, alternatively, concentrating it in vortical structures. We perform local axisymmetric simulations of the COS using the code snoopy, showing first how parasites halt the instability’s exponential growth, and secondly, the different saturation routes it takes subsequently. As the Reynolds and (pseudo-) Richardson numbers increase, the system moves successively from (i) a weakly non-linear state characterized by relatively ordered non-linear waves, to (ii) wave turbulence, and finally to (iii) the formation of intermittent and then persistent zonal flows. In three dimensions, we expect the latter flows to spawn vortices in the orbital plane. Given the very high Reynolds numbers in protoplanetary discs, the third regime should be the most prevalent. As a consequence, we argue that the COS is an important dynamical process in planet formation, especially near features such as dead zone edges, ice lines, gaps, and dust rings.
Highlights
For most of their lives, protoplanetary (PP) discs are too cold and poorly ionised to support a form of the magnetorotational instability unhindered by non-ideal MHD (e.g. Turner et al 2014)
The emergence and collapse of zonal flows from inertial wave turbulence has been witnessed in local simulations of eccentric discs by Wienckers and Ogilvie (2018), who model the phenomena in detail with a predator-prey style of dynamz x
In this paper we have investigated the nonlinear development of the convective overstability (COS) in a local model of a protoplanetary disc
Summary
For most of their lives, protoplanetary (PP) discs are too cold and poorly ionised to support a form of the magnetorotational instability unhindered by non-ideal MHD (e.g. Turner et al 2014). All discs should undergo sharp transitions at special radii, such as dead zone edges, ice lines, gaps, and dust rings where it is likely a strongly decreasing entropy profile might develop It is the goal of this paper to assess the behaviour and vigour of the COS in such special regions. It is possible that, after its initial breakdown, the turbulent flow splits into a sequence of zonal flows, by analogy with semiconvection, leading to a far more vigorous and interesting state (Rosenblum et al 2011, Zaussinger and Spruit 2013) These flows, in turn, may be subject to Kelvin-Helmholtz instability and will shed vortices that could accumulate solids (Lyra 2014, Raettig et al 2021).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
