Aurélien Crida - Indirect terms and the reflex instability : some fun with the inertial forces

Titile: Planet-driven instability in hydrodynamical simulations of protoplanetary disks

Many astrophysical systems are dominated by a more massive object (e.g.: an accretion disk around a star or a black hole, a planetary system...). Such systems are often modeled in a frame centred on this object, which is not the centre of mass. Hence, an inertial acceleration should be applied (often alled "indirect term"). This basic physics is actually more rich, complex, and interesting than it seems, especially in cases where some gravitational interactions can be neglected.

After having defined clearly all the various indirect terms (plural!) and described their role in the dynamics (in particular in the field of planet-disc interactions), I will show that one of them leads to a positive feedback loop between an asymmetry in the disk and the reflex motion of the star. This yields a spectacular exponential growth of the perturbation, which can destabilize a gas disk, and is also connected to the lopsided mode of spiral galaxies.