Joonas Nättilä

Pair Discharges and Radio Emission from Millisecond-Pulsar and White-Dwarf Magnetospheres

Tuomo Salmi, Joonas Nättilä

Coherent radio emission is observed from compact astrophysical objects with relatively weak magnetic fields, including millisecond pulsars and white dwarfs, the latter being proposed as possible sources of long-period radio transients. In such environments, the standard pair discharge mechanism---driven by curvature radiation …

Pair Discharges and Radio Emission from Pulsar Magnetospheres

Joonas Nättilä, Tuomo Salmi

Radio pulsars can power their coherent radio emission through intermittent plasma discharges in magnetospheric gaps. The nonlinear coupling between particle acceleration, quantum electrodynamic (QED) processes, and electric field screening remains difficult to model self-consistently. We present an analytical concurrency model and first-principles …

Turbulence Mode Decomposition and Anisotropy in Magnetically Dominated Collisionless Plasmas

Samuel T. Sebastian, Siyao Xu, Yue Hu, Luca Comisso et autres

Abstract We use 3D fully kinetic simulations to study different turbulence modes and turbulence anisotropy of relativistic turbulence in magnetically dominated collisionless plasmas. We extend the method developed by J. Cho & A. Lazarian for decomposing nonrelativistic magnetohydrodynamic (MHD) turbulence into Alfvén, …

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Turbulence Mode Decomposition and Anisotropy in Magnetically Dominated Collisionless Plasmas

Samuel T. Sebastian, Siyao Xu, Yue Hu, Luca Comisso et autres

We use the 3D fully kinetic simulation to study different turbulence modes and turbulence anisotropy of relativistic turbulence in magnetically dominated collisionless plasmas. We extend the method developed by Cho & Lazarian (2002) for decomposing non-relativistic magnetohydrodynamic (MHD) turbulence into Alfvén, fast, …

QED cross sections in strong magnetic fields

Olavi Kiuru, Joonas Nättilä, Risto Paatelainen, Aleksi Vuorinen

The magnetospheres of magnetars, a class of highly magnetized neutron stars, host magnetic fields exceeding the Schwinger limit, where Quantum Electrodynamics (QED) becomes nonlinear. In such environments, QED scattering processes are strongly modified, which may affect plasma dynamics. In this work, we …

QED cross sections in strong magnetic fields

Olavi Kiuru, Joonas Nättilä, Risto Paatelainen, Aleksi Vuorinen

The magnetospheres of magnetars, a class of highly magnetized neutron stars, host magnetic fields exceeding the Schwinger limit, where Quantum Electrodynamics (QED) becomes nonlinear. In such environments, QED scattering processes are strongly modified, which may affect plasma dynamics. In this work, we …

Statistics of Current and Vorticity Structures in Relativistic Turbulence

Zachary Davis, Luca Comisso, Colby C. Haggerty, Joonas Nättilä

Abstract Coherent structures created through turbulent cascades play a key role in energy dissipation and particle acceleration. In this work, we investigate both current and vorticity sheets in 3D particle-in-cell simulations of decaying relativistic turbulence in pair plasma by training a self-organizing …

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Vlasov methods in space physics and astrophysics

Minna Palmroth, Urs Ganse, Yann Pfau‐Kempf, Markus Battarbee et autres

Abstract This paper reviews Vlasov-based numerical methods used to model plasma in space physics and astrophysics. Plasma consists of collectively behaving charged particles that form the major part of baryonic matter in the Universe. Many physical concepts ranging from our own planetary …

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Statistics of Current and Vorticity Structures in Relativistic Turbulence

Zachary Davis, Luca Comisso, Colby C. Haggerty, Joonas Nättilä

Coherent structures created through turbulent cascades play a key role in energy dissipation and particle acceleration. In this work, we investigate both current and vorticity sheets in 3D particle-in-cell simulations of decaying relativistic turbulence in pair plasma by training a self-organizing map …

Studying the mirror acceleration via kinetic simulations of relativistic plasma turbulence

Saikat Das, Siyao Xu, Joonas Nättilä

Efficient relativistic turbulent acceleration of particles is indicated by recent astrophysical observations. The acceleration mechanism due to temporal variations of magnetic field strengths (``Type II mechanism") remains underexplored. The mirror acceleration has recently been proposed as an efficient Type II mechanism for …

Machine Learning Characterization of Intermittency in Relativistic Pair Plasma Turbulence: Single and Double Sheet Structures

Trung Ha, Joonas Nättilä, Jordy Davelaar, Lorenzo Sironi

Abstract The physics of turbulence in magnetized plasmas remains an unresolved problem. The most poorly understood aspect is intermittency—spatiotemporal fluctuations superimposed on the self-similar turbulent motions. We employ a novel machine learning analysis technique to segment turbulent flow structures into distinct clusters …

aweSOM: a CPU/GPU-accelerated Self-organizing Map and Statistically Combined Ensemble Framework for Machine-learning Clustering Analysis

Trung Ha, Joonas Nättilä, Jordy Davelaar

Ha et al., (2025). aweSOM: a CPU/GPU-accelerated Self-organizing Map and Statistically Combined Ensemble Framework for Machine-learning Clustering Analysis. Journal of Open Source Software, 10(108), 7613, https://doi.org/10.21105/joss.07613

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