Researchers at Tohoku University and Utsunomiya University have made a breakthrough in understanding the complex nature of turbulence in structures called “accretion disks” surrounding black holes, using state-of-the-art supercomputers to conduct the highest-resolution simulations to this point. An accretion disk, because the name implies, is a disk-shaped gas that spirals inwards towards a central black hole.
There’s an ideal interest in studying the unique and extreme properties of black holes. Nonetheless, black holes don’t allow light to flee, and due to this fact can’t be directly perceived by telescopes. With a purpose to probe black holes and study them, we have a look at how they affect their surroundings as an alternative. Accretion disks are one such approach to not directly observe the consequences of black holes, as they emit electromagnetic radiation that may be seen by telescopes.
“Accurately simulating the behaviour of accretion disks significantly advances our understanding of physical phenomena around black holes,” explains Yohei Kawazura, “It provides crucial insights for interpreting observational data from the Event Horizon Telescope.”
The researchers utilized supercomputers resembling RIKEN’s “Fugaku” (the fastest computer on the earth up until 2022) and NAOJ’s “ATERUI II” to perform unprecedentedly high-resolution simulations. Although there have been previous numerical simulations of accretion disks, none have observed the inertial range due to lack of computational resources. This study was the primary to successfully reproduce the “inertial range” connecting large and small eddies in accretion disk turbulence.
It was also discovered that “slow magnetosonic waves” dominate this range. This finding explains why ions are selectively heated in accretion disks. The turbulent electromagnetic fields in accretion disks interact with charged particles, potentially accelerating some to extremely high energies.
In magnetohydronamics, magnetosonic waves (slow and fast) and Alfvén waves make up the fundamental forms of waves. Slow magnetosonic waves were found to dominate the inertial range, carrying about twice the energy of Alfvén waves. The research also highlights a fundamental difference between accretion disk turbulence and solar wind turbulence, where Alfvén waves dominate.
This advancement is anticipated to enhance the physical interpretation of observational data from radio telescopes focused on regions near black holes.
The study was published in Science Advances on August 28, 2024.
