Seminario DAS: Simulating the magnetorotational instability in low-luminosity accretion disks

Speaker: Dr. Mario Riquelme
Affiliation: Professor, FCFM, Universidad de Chile

Abstract: Low-luminosity accretion disks around compat objects have recently attracted significant attention. Two important examples are the disks around the supermassive black holes Sgr A* and M87*, whose high resolution observations by the Event Horizon Telescope (EHT) and by other observatories have motivated major theoretical efforts to model their emission. An important characteristic of these disks is that the plasma being accreted is expected to be "collisionless", meaning that the energy dissipated in the disk does not have enough time to be thermalized. This gives rise to several observable non-thermal phenomena, including different heating rates for the different plasma species and particle acceleration to ultra-relativistic energies. Kinetic plasma simulations that go beyond fluid (MHD) modeling are thus needed in order to acquire a first-principles picture of these non-thermal processes and to predict their observational signatures.

In this talk, we will present our initial results from 2D and 3D fully kinetic, particle-in-cell (PIC) plasma simulations of the collisionless magnetorotational instability (MRI), an instability expected to play a crucial role in regulating energy dissipation and outward transport of angular momentum in accretion disks. Our results show that the overall dynamics of the collisionless MRI is similar to the one of its fully collisional counterpart. However, its non-thermal effects are significant and potentially observable. We will discuss possible applications of these types of studies to future observations of low-luminosity accreting systems.