Toroidal vortices and the conglomeration of dust into rings in protoplanetary discs (article)

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.The dataset associated with this journal article can be found in ORE at http://hdl.handle.net/10871/18340We identify a new hydrodynamical instability in protoplanetary discs that may arise due to variations in the dust-to-gas ratio and may lead to concentration of dust grains within a disc. The instability can arise due to dust settling, which produces a vertical compositional entropy gradient. The entropy gradient drives a baroclinic instability that is capable of creating toroidal gas vortices that gather dust into rings. Such dust rings are potentially observable via continuum emission of the dust or scattered light. Indeed, this instability may offer an explanation for the rings recently observed in the discs around the young stars HL Tau and TW Hya that does not rely on clearing by protoplanets. The instability may also have wider ramifications, potentially aiding dust agglomeration, altering the radial migration of larger planetesimals, and modifying angular momentum transport within a disc.Science and Technology Facilities Council (STFC)European Research Council - European Community's Seventh Framework Programme (FP7/2007-2013)BIS National E-Infrastructure capital grantSTFC DiRAC Operations gran