2025 Simons Collaboration on Extreme Electrodynamics of Compact Sources Annual Meeting

Richard Anantua
University of Texas, San Antonio

Hidden Figures – Towards EHT-Scale Signatures of Positrons and Axions

General relativistic magnetohydrodynamic simulations evolve realistic plasma inflows and outflows in jet/accretion flow/black hole (JAB) systems and, coupled with postprocessors with general relativistic ray tracers, enable us to test radiating particle energetics and composition against horizon-scale data for active galactic nuclei (AGN) such as M87. Using the “Observing” JAB Simulations methodology, we include positrons into ray-traced models of SANE and MAD HARM simulations of M87 with turbulent heating to find distinguishable Faraday-effect-mediated positron signatures. We then lay the groundwork for applying the “Observing” JAB Simulations methodology to detecting signatures of superradiant axion production around supermassive black holes given astrophysical confounds and a novel application of primordial black holes accreting positronium in KORAL simulations in the first few seconds of the universe under magnetorotational instability to grow into a substantial fraction of dark matter in the present day.
 

Andrei Beloborodov
Columbia University

Fast Radio Bursts and Extreme Electromagnetism

Fast radio bursts (FRBs) are the strongest observed electromagnetic waves in the universe. They are likely generated by magnetized neutron stars and carry information about unusual and extreme phenomena. This talk will describe attempts to understand the bizarre physics of ultrastrong electromagnetic waves, their vulnerability, their impact on a surrounding medium, and a possible mechanism of their generation. In addition to FRBs from isolated neutron stars, similar electromagnetic phenomena can be triggered in tight binary systems and accompany gravitational waves from their mergers.
 

Stanislav Boldyrev
University of Wisconsin, Madison

Alfvénic Turbulence and Particle Acceleration in a Relativistic Magnetically Dominated Plasma

The properties of strong Alfvénic turbulence in a magnetized relativistic collisionless plasma are examined. This type of turbulence is common in astrophysical plasmas and plays a significant role in energizing plasma particles. At smaller scales, it creates intermittent current structures and can be affected by tearing instability. In magnetically dominated environments, Alfvénic turbulence acts as an effective mechanism for the nonthermal acceleration of particles. The relative strength of turbulent magnetic fluctuations, compared to the guiding magnetic field, impacts the energy spectrum of the accelerated particles. Furthermore, it influences the distribution of the pitch angles of the particles, which may affect the radiative signatures of astrophysical objects.
 

Matt Caplan
Illinois State University

Diffusion and Vortices in Strongly Coupled Plasmas

The mechanical properties of neutron star crust ultimately influence astrophysical emissions. Elastic moduli and transport coefficients in the solid are therefore essential microphysics input for modeling and understanding observations. Diffusion coefficients in strongly coupled plasmas are especially important for characterizing crustal elasticity but are challenging to calculate. Using molecular dynamics simulations, we have characterized diffusion in Yukawa crystals near melting, and in addition, we will show how vortex pinning and unpinning in the crust may ultimately involve diffusive processes requiring new coupled codes.
 

Frederico Fiúza
Instituto Superior Técnico, Lisbon

Extreme Plasma Physics: From Astrophysics to the Laboratory

Extraordinary discoveries related to neutron stars and black holes are opening new scientific frontiers that challenge our current knowledge of plasmas under extreme conditions and demand multi-disciplinary approaches. Recent advances in high-intensity lasers and particle beams are now enabling the generation of relevant high-energy-density and strong-field conditions in the laboratory. This is creating unique opportunities to probe the basic processes that control plasma dynamics and radiation emission in these extreme environments and benchmark theoretical and numerical models. Frederico Fiúza will discuss some of the main challenges, recent progress and exciting opportunities in this field.
 

Noémie Globus
IA-UNAM, Stanford University

Magnetic Keys to a Cosmic Puzzle

What are the sources of ultra-high-energy cosmic rays (UHECR), the most energetic particles we observe? The field of UHECR has been greatly advanced in the Auger and Telescope Array era, but the answer to this question is still unknown. Noémie Globus will discuss two magnetic “keys” to solving this cosmic puzzle. The first “key” is the role magnetic fields play in the acceleration processes, from the ordered magnetic fields around neutron stars and black holes to the turbulent magnetic fields at astrophysical shocks. The second “key” is the role magnetic fields play in cosmic-ray propagation in our galaxy and in the extragalactic medium. Globus will show how solving these keys will possibly unlock the door to our understanding of future UHECR observations, which may help us to identify the sources.
 

Sam Gralla
University of Arizona

Strong-Field Limits of Plasma Dynamics

Many of the most spectacular astrophysical phenomena are connected with plasma in strong magnetic fields. In this extreme field limit, all conceivable descriptions of the plasma reduce to the universal, simpler theory of force-free electrodynamics. However, the underlying plasma microphysics is essential for astrophysical modeling, since it impacts the boundary conditions for the force-free solution and determine the small corrections that influence observables. Sam Gralla will give a general overview of the strong-field limit and discuss two general approaches (top-down and bottom-up) for incorporating the underlying microphysics. Gralla will then describe a staggered perturbation approach to modeling systems in the strong-field limit, which are implemented using a two-fluid description. This approach has the potential to provide global magnetosphere models without the need for global particle-in-cell simulations
 

Yajie Yuan
Washington University, St. Louis

Nonlinear Plasma Wave Dynamics in Magnetar Magnetospheres

Magnetars are a special type of neutron star with the most intense magnetic fields known — reaching up to 100 gigatesla. They are usually young and active, powering a range of energetic transient events, from X-ray bursts to giant flares in soft gamma-rays, and possibly even fast radio bursts. One proposed trigger behind some of the transients is crustal activities (like starquakes) that launch plasma waves into the magnetosphere, most notably the Alfvén waves — a transverse wave that propagates along the magnetic field. The waves undergo several interesting nonlinear processes in the magnetosphere, potentially powering the bright, multiwavelength signals we observe. In this talk, Yajie Yuan will outline our systematic study of these nonlinear processes and show how a deeper understanding of plasma-wave dynamics can shed light on the extreme electrodynamics that govern magnetars and their remarkable emissions.