Researchers have made a groundbreaking discovery in the field of black hole astrophysics, unveiling the mechanisms behind the acceleration of charged particles in the turbulent environments surrounding these enigmatic cosmic giants.
Simulating the Unseen
Now, scientists at KU Leuven, the University of Colorado Boulder, the Flatiron Institute and University of Wisconsin–Madison are attempting to address one lingering question in black hole astrophysical theory: Can charged particles orbiting or falling into turbulent flows around such cosmic wonders be churned up to speeds approaching light?
To solve this problem, the team started by simulating turbulent flows in the extreme conditions around black holes. These are environments in which the magnetorotational instability (MRI), a potent magnetic-field amplification process that naturally operates in plasmas subjected to the shears and forces near black holes, is expected to be effective.
The researchers used simulations to follow the MRI from its evolution up to the turbulent stage and study the acceleration of charged particles in this turbulence. But they soon learned that in the all-turbulent case, even though it was self-sustaining and there were no discernible boundaries, because the particles at that point had been engulfed by the prior dynamical history en route to turbulent set-up it nearly impossible to disentangle the impact of newly added turbulence.
A Breakthrough Approach
The scientists therefore decided to remove the pre-turbulence effects and focus solely on the motion of particles during turbulent phase, using a technique that had not been previously implemented. Using physically based radiative dynamics that effectively suppress the influence of pre-turbulence stages, the authors were able to constrain their analysis solely on the acceleration of particles within the turbulence.
But it was not over. While this provides useful information for other researchers in studying these dynamical public goods games, to answer the team’s original question they also needed to carry out a simulation of a system large enough that it can qualitatively mimick MRI behaviour realistically Earlier attempts with smaller simulation sizes were found not feasible, and the MRI did not develop turbulence.
The researchers used the Argonne Leadership Computing Facility (ALCF) to run their computer code on more than 250,000 CPUs for several weeks nonstop. This computational power was enough to allow them to model a system that is large enough to include the intricate MRI-driven turbulence, with its subsequent impact on particle acceleration.
Conclusion
The signature pillar of paper led by Bacchini provides new insights into the enigmatic events around black holes. With their research into particle acceleration in MRI-driven turbulence, the team have contributed an important advance of knowledge in these extreme environments.
The research has wider implications than black hole astrophysics, too, showing how the radiation around these cosmic behemoths is produced. Ultimately, this knowledge could be used to test Einstein’s theory of general relativity in new ways and lead to a deeper understanding of some of the most mysterious phenomena in the universe.
