Oral Presentation
The critical role of magnetic field for the formation of protoplanetary disk formation
Presenter: Patrick Hennebelle (CEA Saclay)
We have carried out a series of collapse calculations which include the effect of magnetic field in the presence of the non-ideal mhd ambipolar diffusion. A broad range of initial conditions has been explored in terms of rotation, turbulence, mass and magnetization (Masson et al. 2016, A&A, Hennebelle et al. 2016, ApJ). We also develop an analytical model aiming at predicting the radius of the disks which form. We find, both analytically and numerically that the protoplanetary disks are remarkably self-regulated by non-ideal MHD processes. That is to say the disk radius is remarkably insensitive to the initial parameters of the dense core (in terms of turbulence, rotation and magnetic intensity as along as it is not too small).
We have compared our analytical model with the simulation results and found that they agree within a factor of about 2.
This unexpected behavior, which is at complete variance form the hydrodynamcial case is a consequence of magnetic braking and magnetic diffusivity. In this context, turbulence is clearly of secondary importance.
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