The impact of the co-orbital flow on protoplanetary migration

Abstract: Forming planets experience a strong tidal interaction with the gaseous protoplanetary disk in which they are embedded. This interaction drives in particular a radial migration of the planet, so that its orbit may shrink or expand by several orders of magnitude over the disk lifetime. I will review the different types of migration studied thus far, and I will put special emphasis on the dynamics of the coorbital region and the so-called corotation torque. This torque can play a very important role in several circumstances: at a cavity edge (planetary trap), in a massive disk when the planet depletes partially its co-orbital region (type III migration), or when the flow behaves adiabatically over a dynamical timescale: the corotation torque is then found to depend on the disk’s radial entropy gradient. Lastly, I will show that a low-mass protoplanet subjected to planetesimal bombardment, which heats its surrounding disk, experiences an additional, positive torque component, comparable in magnitude to the wake’s torque.