General Relativistic numerical models of accretion disks and magnetic reconnection with the PLUTO code

Magnetic fields shape the dynamics of relativistic plasmas that orbit around astrophysical black holes (BHs), as observed in current general relativistic magnetohydrodynamic (GRMHD) models.

A primary example is magnetic reconnection, i.e. the rearrangement of the structure of magnetic field lines, which converts magnetic energy into kinetic and thermal energy and accelerates particles to relativistic velocities, thus producing the high-energy non-thermal radiation observed from accreting compact objects.

Despite the importance of small-scale instabilities in determining the properties of magnetic dissipation and particle acceleration, global simulations of relativistic accretion disks usually consider either infinitely conducting fluid or one with a constant finite magnetic dissipation, which doesn't capture the collisionless nature of astrophysical plasmas.

The goal of the GR-PLUTO project is to perform the first GRMHD numerical study on reconnection in relativistic disks using an effective non-constant resistivity, which will go beyond standard fluid models by introducing new non-collisional effects in global GRMHD simulations.

This approach will test our current knowledge of relativistic magnetic reconnection and provide more consistent estimates for the rate at which particles can be accelerated, along with the general structure of magnetized accretion flows around BHs where this process occurs.

As the simulations required to quantify the improvements w.r.t. state-of-the-art relativistic MHD reconnection and GRMHD accretion flow models have a high computational cost, the action will include the development of a numerical tool for the modeling of GRMHD flows based on the public PLUTO code.

In collaboration with the hosting group at UniTo, the action will produce a new code that will combine the benefits of highly accurate numerical schemes with energy-efficient HPC methods, which will continue to be freely accessible by the public.