Menu:

Research

My research interests focus on accretion discs physics, turbulence, dynamo action and planet formation. You'll find in these pages some informations about these researches plus some flash movies (just click on the snapshots to see the videos). The links below will direct you to a specific topic.
Dynamics and evolution of protoplanetary discs
Cataclysmic variables

Dynamics and evolution of protoplanetary discs

It is often assumed that the magnetorotational instability (MRI), a magnetic instability, is responsible for the generation of turbulence in accretion discs. However, in planet-forming discs, also known as protoplanetary discs, the temperature is so low that the gas is not a good electrical conductor. It is therefore important to take into account the finite conductivity of the plasma, which is modelled as non-ideal magneto-hydrodynamical (MHD) effects. These effects have a dramatic impact on the dynamics of the disc: the MRI disappears and one is left with a mostly laminar disc.

How can one explain that these discs are still accreting then? That's the question I have been adressing with Matt Kunz (Princeton) and my PhD student William Bethune. For us, the answer lies in the presence of large scale magnetic winds, which are sufficient to drive accretion at the disc surface. We have demonstrated this process by performing the first fully global non-ideal MHD simulation of a protoplanetary disc in 2017 (see movie below).

In addition to accretion, we have been looking for hints of large scale structures, such as rings and gaps, as seen in recent ALMA and VLT observation. To our surprise, we found that magnetic effects in the non-ideal regime were driving self-organisation in the disc, forming structures that are very similar to the ones we see in our telescopes! There is still a long way to demonstrate that what our simulations are predicting is actually what we are seeing, but we've never been so close...

Above: 3D simulation of a protoplanetary disc in the region 10-100 au including all of the non-ideal MHD effects. This proof of concept demonstrates the presence of large scale winds driving accretion and of self-organisation.

Cataclysmic variables

Above: 2D simulation of a cataclysmic variable. The simulation is computed in the frame rotating with the system. The companion star is therefore on the right and stellar material starts to fall on the white dwarf and forms an accretion disc.