Astrophysical Plasmas from the Sun to Black Holes | 9am Tue, Feb 3, 2026

[Grigory Bronevetsky]

Modeling Talks

Astrophysical Plasmas from the Sun to Black Holes Fabio Bacchini, KU Leuven Tues, Feb 3, 2026 | 9am PT Meet | Youtube Stream Hi all, The presentation will be via Meet and all questions will be addressed there. If you cannot attend live, the event will be recorded and can be found afterward at https://sites.google.com/modelingtalks.org/entry/astrophysical-plasmas-from-the-sun-to-black-holes More information on previous and future talks: https://sites.google.com/modelingtalks.org/entry/home Abstract: Everybody knows that matter on Earth can be commonly found in three states: solid, liquid, and gas. But if we consider the Universe in which we live, 99% of all matter exists in a fourth state, called "plasma": a gas so hot and dilute that electrons are free to escape the electric pull of atomic nuclei. All the stars in the Universe are made of plasma, which also fills the interstellar and intergalactic space; plasmas are also found around black holes and neutron stars; and gigantic jets of plasma moving nearly at the speed of light protrude from the center of many galaxies and extend for hundreds of thousands of light years. Studying astrophysical plasmas is then of prime importance to understand many fundamental processes occurring everywhere in our Universe.  And yet, the study of plasmas is often very difficult: the equations that govern the plasma dynamics are extremely complicated, and usually can only be solved with the help of supercomputers carrying out calculations on thousands of CPUs. In this talk, I will review the basic theory of plasmas, by linking to phenomena that we commonly observe in many astrophysical environments, from our own Sun to the surroundings of supermassive black holes. I will describe the governing equations of plasma dynamics, and then move onto more detailed topics: the Sun's atmosphere, the solar wind and the Earth's magnetosphere, and the surroundings of black holes and neutron stars. Bio: Fabio Bacchini  is Assistant Professor at the Centre for mathematical Plasma Astrophysics of KU Leuven (Belgium). In his work, he designs and applies numerical simulations on supercomputers to address the most relevant questions in astrophysics concerning space plasmas. His research covers a wide range of astrophysical scenarios, from the heliosphere and near-Earth environment to the surroundings of black holes and neutron stars.

[Grigory Bronevetsky]

Video Recording: https://youtube.com/live/4RPflLnj_Aw

Slides: https://drive.google.com/file/d/1XvH7sVfC859OUYzYuiY86vIJnD7b96WS/view?usp=sharing

Summary:

• Plasma dynamics: 

• Atomic ions (nuclei with some/all electrons stripped off) and free electrons

• 99% of matter in universe is a plasma

• Examples: auroras, lightning, plasma balls, nuclear fireballs, neon signs, welding arcs

• Nuclear fusion: 2 small atoms (e.g. Hydrogen) fused into a larger one (e.g. Helium)

• Magnetic confinement: use magnetic fields to confine Hydrogen nuclei into a small space at high temperature where they’ll collide and fuse

• Since they’re charged and energetic they act in complex ways that are hard to model and manage

• Plasmas in Space:

• Sun: giant ball of plasma

• Interplanetary/galactic space is filled with diffuse plasma

• Black holes surrounded by plasma

• Focus: stellar plasmas

• Sun’s surface has regular explosions that blow out plasma

• These plasma eruptions often hit the Earth

• Earth’s magnetic field protects the Earth because it bends the path of the plasma, which is charged

• When the diverted plasma particles end up hitting the Earth, we see auroras and can get disruptions to satellites, ground electronic systems

• Multiscale spatial scales of plasma

• Black hole:

• Jets of gas coming out of a galaxy’s central black hole: 10k light years in length

• Plasma around a black hole: 40b km wide

• Plasma turbulence dynamics: ~1km long

• Stars:

• Coronal ejections

• Complex internal structure: terminal shock, magnetic trap (XRay emissions from trapped gas), reconnection outflows (particle accelerated radiation)

• Plasma simulations to understand dynamics

• Plasma behavior is described by a complex set of equations: 

• magnetic/electric forces

• contact forces of fluid, etc.

• Aggregated fluid-level

• Individual particle-granularity

• May incorporate relativistic dynamics (key in high gravity and energy regimes)

• Used to predict behavior of plasmas and design devices that interact and control them

• Range in scale from microseconds to billions of years

• Whole universe simulation

• Black holes

• Neutron stars

• Supercomputing for plasma simulation

• Need (hundreds of) thousands CPUs and GPUs

• Hard to access and significant environmental impact

• Scales: Micro->Meso->Macro

• Regimes: Kinetic->Hybrid->Fluid

• Energy: Newtonian->Transrelativistic->Relativistic

• The location of use-case in above matrix determines the details that a simulation must incorporate

• Examples:

• Low energies: Heliosphere

• Main structures: corona, wind, planetary magnetospheres

• Phenomena: coronal mass ejections, wind, turbulence

• Macro/Fluid/Newtonian

• High energies: Black holes

• High gravitational field bends spacetime and the path of light and matter

• Show paths of all particles that leave, collapse into or permanently orbt

• High energies, Large scales: BH/NS Magnetosphere: Macro/Fluid/Relativistic

• High Energies/Small Scales: collisionless accretion and coronal acceleration:

• Particle acceleration

• Emission of X-Rays and Gamma Rays

• Micro-Meso/Kinetic/Trans-Relativistic

• High energies at mesoscales:

• Fluid simulations where you place particles into the dynamics and trace their paths

• Must account for relativity and small-scale kinetic effects

• Meso/Hybrid-Kinetic/Trans-Relativistic

• Simulations validated by 

• Comparing predicted energy emission spectra (especially X-rays) to real observations

• Neutrino emissions

• Timescales of events simulated vs astronomical observations