Research Center for Astronomy


15-20 September 2024

@ Academy of Athens



Tuesday 16 July 2024, 12:00


Buckling instability in galactic bars

Ewa L. Lokas

Nicolaus Copernicus Astronomical Center, Warsaw


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Featured Picture

Relativistic magnetohydrodynamics simulation


Three-dimensional view of the magnetization (σ) from a general relativistic magnetohydrodynamics simulation. The rest-mass density is depicted exclusively on the equatorial plane to visualize the disk's rotation (with a disc radius of 30 rg). The magnetization color code ranges from 1.00 to 1.20, highlighting highly magnetized regions with σ > 1.15 as plasmoids. Inset: A close-up view of the largest plasmoid within the snapshot; magnetic fields outside the plasmoid are shown in green, while those inside are cyan. Magnetic field lines inside the plasmoid are tangled and are expected to have a distribution of high energy particles radiating and observed as a black hole flare. Plasmoids, magnetic structures of various sizes and lifetimes, play pivotal roles in our study. We have identified three distinct launching sites for these plasmoids: the low-density funnel, the turbulent interior of the disk, and the jet sheath. Each site yields plasmoids with unique characteristics and dynamics. Here, we observe at least two plasmoids, each exhibiting a non-spherical, filamentous morphology, influenced by the shearing motion in the background flow. Smaller plasmoids are frequently generated but either accrete onto the black hole or are swiftly destroyed by shear forces. In contrast, larger plasmoids, surviving for longer duration, are rare occurrences. Our simulations reveal that no plasmoids persist beyond a spherical region approximately 30 rg from the black hole's event horizon. Beyond this boundary, all plasmoids transform into high-temperature clouds, gradually cooling over time. This comprehensive analysis offers valuable insights into the complex dynamics and fates of plasmoids in our simulated environment, contributing to a deeper understanding of astrophysical phenomena.

Reference: Nathanail, A., Mpisketzis, V., Porth, O., Fromm, C. M. Rezzolla, L. Magnetic reconnection and plasmoid formation in three-dimensional accretion flows around black holes,Monthly Notices of the Royal Astronomical Society, Volume 513, Issue 3, pp.4267-4277 July 2022

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