Resources

"On the origin of spectral bands in Crab radio emission"

By: M.V. Medvedev, Phys. Rev. Lett. 133, 205201 

The paper solves a 20-year-old puzzle of the Crab pulsar, and introduces a novel astrophysical "diagnostic" method, which allows one to obtain high-resolution "tomography" data of a pulsar magnetosphere. The model explains the peculiar spectral band structure of the high-frequency interpulse of the Crab pulsar radio emission as diffraction fringes created by the pulsar’s plasma-filled magnetosphere, acting as a frequency-dependent diffraction screen.

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“Ohm’s Law, the Reconnection Rate, and Energy Conversion in Collisionless Magnetic Reconnection”

By: Yi-Hsin Liu et al., Space Sci. Rev., 221, 16 (2025)

Magnetic reconnection is a nonlinear, dynamical process that involves electromagnetism, magnetic field geometry/topology, and complex charged particle motions in a multi-dimensional, multiscale system, where physics occurring at a singular point can lead to tremendous energy release at the macroscale. For these reasons, the study of magnetic reconnection has been a fascinating and challenging subject since 1953. This review article focuses on the progress in the past 20 years on collisionless reconnection study, where kinetic simulations and in-situ spacecraft observations have accelerated our understanding. We expect it also serves as a helpful tutorial for graduate students and early career scientists.

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"Proton Acceleration in Low-β Magnetic Reconnection with Energetic Particle Feedback"

By: Jeongbhin Seo, Fan Guo, Xiaocan Li, and Hui Li, ApJ

Density (left) and energy spectrum (right) of energetic particles generated by low-beta magnetic reconnection. The feedback effect becomes stronger from red to blue.

Through this study, we addressed how feedback from nonthermal energetic particles influences the dynamics and particle acceleration in magnetic reconnection. We found that nonthermal particles are accelerated during reconnection, producing a power-law energy spectrum. The feedback from these particles suppresses highly compressed structures in the reconnection layer, resulting in a steeper energy spectrum. This feedback remains effective even with isotropic momentum distributions. These results underscore the importance of incorporating nonthermal particle feedback in simulations to accurately model magnetic reconnection and particle acceleration, enhancing our understanding of particle energization in solar and astrophysical plasmas.

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Lab Confirms Fundamental Theory on Planet and Star Formation

By: Y. Wang, E. P. Gilson, F. Ebrahimi, J. Goodman, and H. Ji, Phys. Rev. Lett.

Figure 1: The SMRI is considered essential in the plasma flowing orbiting around a black hole (left). The experiment (right) features two concentric cylinders with a gap filled with galinstan, a liquid-metal alloy. The cylinders rotate at different speeds, with split end caps spinning at intermediate rates. An axial moderate-strength magnetic field is applied to trigger SMRI. Adapted by APS/Carin Cain

Scientists at the Princeton Plasma Physics Laboratory have achieved the first experimental confirmation of the Standard Magnetorotational Instability (SMRI), a crucial magnetohydrodynamic process that drives the collapse of accretion disks into planets, stars, and black holes. SMRI facilitates the outward transfer of angular momentum, allowing inner material to spiral inward. Using an innovative Taylor-Couette flow experiment—featuring rotating cylinders and liquid metal in a magnetic field—researchers detected signatures of the axisymmetric SMRI[1], validating long-standing theoretical predictions. Additionally, they discovered the non-axisymmetric SMRI[2] and unveiled a new excitation mechanism[3]. These breakthroughs highlight the power of laboratory astrophysics in complementing space observations to unravel fundamental cosmic mysteries.

References: 

Y. Wang, E. P. Gilson, F. Ebrahimi, J. Goodman and H. Ji, Observation of axisymmetric standard magnetorotational instability in the laboratory, Phys. Rev. Lett. 125, 115001 (2022). DOI: https://doi.org/10.1103/PhysRevLett.129.115001

Y. Wang, E. P. Gilson, F. Ebrahimi, J. Goodman, K. J. Caspary, H. W. Winarto and H. Ji, Identification of a non-axisymmetric mode in laboratory experiments searching for standard magnetorotational instability, Nat. Comm. 13, 4679 (2022). DOI: https://doi.org/10.1038/s41467-022-32278-0

Y. Wang, F. Ebrahimi, Hongke Lu, J. Goodman, E. P. Gilson, and H. Ji, Observation of nonaxisymmetric standard magnetorotational instability induced by a free-shear layer, arXiv:2411.02361 (2025). DOI: https://doi.org/10.48550/arXiv.2411.02361

"Multispecies Ion Acceleration in 3D Magnetic Reconnection with Hybrid-Kinetic Simulations"

By: Qile Zhang et al., Phys. Rev. Lett. 132, 115201

This work reveals new insights into particle injection/acceleration for multiple ion species in magnetic reconnection, while most previous theoretical/numerical studies are limited to electrons/protons. We perform the first 3D hybrid simulations (kinetic ions, fluid electrons) that contain sufficient scale separation to model the computationally-challenging heavy-ion acceleration. For the first time, these simulations demonstrate simultaneous acceleration of all available ion species into power-law spectra, with similar indices but different maximum energy – involving a common Fermi-acceleration process with delayed onset for lower-charge-mass-ratio ions. These results are consistent with in-situ observations, essential to understand the critical fundamental problem of particle acceleration in reconnection.

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"Plasmoid Formation and Strong Radiative Cooling in a Driven Magnetic Reconnection Experiment” 

By: R. Datta et al., Phys. Rev. Lett. 132, 155102 (2024)

In many astrophysical environments, strong radiative cooling competes with heating processes such as magnetic reconnection, which converts magnetic energy into thermal and kinetic energy. This cooling can lead to instabilities inside the reconnection layer, including the complete radiative collapse of the layer. In recent experiments on the world’s largest pulsed-power facility, the Z Machine at Sandia National Laboratories, researchers studied radiatively cooled reconnection in the laboratory. Among other observations, they were able to study the formation, dynamics, and eventual collapse of plasmoids (a secondary tearing instability within the reconnection layer) using an ultra-fast X-ray camera. 

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