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SUMMARY:Corotation and Wave Torques on Low-Mass Planets in Protoplanetary 
 Discs - Josh Brown (DAMTP)
DTSTART:20231121T140000Z
DTEND:20231121T150000Z
UID:TALK208570@talks.cam.ac.uk
CONTACT:Roger Dufresne
DESCRIPTION:In young extrasolar systems\, planets embedded within gaseous 
 protoplanetary discs experience strong gravitational interactions with the
  disc\, causing the planet to migrate inwards or outwards on a timescale f
 ar shorter than the disc’s lifetime. Understanding the strength and sign
  of the torque exerted by the disc on the planet as a function of the disc
 ’s parameters is therefore essential for predicting and understanding ex
 trasolar system architectures.\n \nThe flow induced by an Earth-mass plane
 t admits a particularly elegant linearisation and solution. This involves 
 large-scale excited spiral density waves which transport angular momentum 
 radially away from the planet\, and ‘horseshoe orbits’ within a critic
 al layer which allow fluid elements on similar orbital radii to the planet
  (that is\, corotating fluid elements) to periodically exchange angular mo
 mentum with the planet.\n \nThe total torque on the planet may be expresse
 d in terms of these angular momentum dynamics\, and depends at leading ord
 er on the local surface density and temperature gradients of the disc\, as
  well as a factor arising from the cylindrical geometry. We derive novel e
 quations which capture uniformly the dynamics of potential vorticity and e
 ntropy within the critical layer\, as well as the larger scale excited den
 sity wave structure. Importantly\, this resolves the previously overlooked
  significant density wave excitation induced by entropic effects at corota
 tion. The result is a more robust calculation of the torque on an Earth-ma
 ss planet.
LOCATION:MR14 DAMTP and online
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