Researchers at Tohoku University and Utsunomiya University have made a breakthrough in understanding the complex nature of turbulence in so-called accretion disks around black holes. Using state-of-the-art supercomputers, they have carried out simulations with the highest resolution to date.
An accretion disk is, as the name suggests, a disk-shaped gas that spirals inward toward a central black hole.
There is great interest in studying the unique and extreme properties of black holes. However, black holes do not allow light to escape and therefore cannot be directly observed by telescopes.
To study and explore black holes, we instead study how they affect their surroundings. Accretion disks are one way to indirectly observe the effects of black holes, as they emit electromagnetic radiation that is visible with telescopes.
“The precise simulation of the behavior of accretion disks contributes significantly to our understanding of the physical phenomena surrounding black holes,” explains Yohei Kawazura. “It provides crucial insights for the interpretation of observational data from the Event Horizon Telescope.”
The researchers used supercomputers such as RIKEN’s Fugaku (the world’s fastest computer until 2022) and NAOJ’s ATERUI II to perform simulations at unprecedented high resolution.
The study was published in Scientific advances on August 28, 2024.
Although there have been previous numerical simulations of accretion disks, none have been able to observe the inertial region due to a lack of computational resources. This study was the first to successfully reproduce the “inertial region” connecting large and small vortices in accretion disk turbulence.
In addition, this region was found to be dominated by “slow magnetosonic waves.” This discovery explains why ions in accretion disks are selectively heated. The turbulent electromagnetic fields in accretion disks interact with charged particles, possibly accelerating some of them to extremely high energies.
In magnetohydrodynamics, magnetosonic waves (slow and fast) and Alfvén waves form the fundamental wave types. Slow magnetosonic waves have been found to dominate the inertial region and carry 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 advance is intended to improve the physical interpretation of observational data from radio telescopes aimed at regions near black holes.
Further information:
Yohei Kawazura et al, Inertial region of magnetorotational turbulence, Scientific advances (2024). DOI: 10.1126/sciadv.adp4965
Provided by Tohoku University
Quote: Supercomputer simulations reveal nature of turbulence in black hole accretion disks (29 August 2024), accessed 29 August 2024 from https://phys.org/news/2024-08-supercomputer-simulations-reveal-nature-turbulence.html
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