From non-ideal magnetohydrodynamics to the structure and evolution of protoplanetary discs – MHDiscs

Circumstellar discs are the birthplaces of planets. They form around young protostars and dissipate in a few million years. Modern submillimeter and optical telescopes such as ALMA and VLT/SPHERE are now able to resolve thin structures in the bulk of these objects, such as rings, crescents or spirals, probing the very origin of planetary systems similar to our own.

Our current understanding of these discs relies on a very crude modelling of a hypothetic magneto-hydrodynamic (MHD) turbulence thought to play an essential role in the evolution and structure of these systems. However, there is now compelling theoretical evidence that these discs are weakly turbulent, if not laminar, because of their low ionisation fraction and thus poor coupling to the magnetic field. This suggests that subtle MHD processes are driving the dynamics of these objects. Moreover, my recent theoretical breakthroughs demonstrate that these gaseous discs can self-organise, spontaneously creating thin structures surprisingly similar to the ones we observe.

I propose that computing global non-ideal MHD models from massively parallel numerical simulations will shed a new light on these observations, connecting the long-term evolution of these objects to the formation of large-scale structures seen by ALMA and SPHERE. We expect MHDiscs to provide reliable global evolution models by coupling gas dynamics to dust and irradiation, which will be used to produce accurate synthetic observations. We will test our models by comparing our predictions to observational constraints (spectral energy distribution, dust spatial distribution, emissivity contrast), setting the stage for a deeper understanding of the formation of planetary systems.