Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1412.1966

Guiding-center transformation of the radiation-reaction force in a nonuniform magnetic field

Eero Hirvijoki·Joan Decker·Alain Brizard·Ola Embréus
View original source ↗Read source document ↗Export metadata ↓

Abstract

In this paper, we present the guiding-center transformation of the radiation-reaction force of a classical point charge traveling in a nonuniform magnetic field. The transformation is valid as long as the gyroradius of the charged particles is much smaller than the magnetic field nonuniformity length scale, so that the guiding-center Lie-transform method is applicable. Elimination of the gyromotion time scale from the radiation-reaction force is obtained with the Poisson bracket formalism originally introduced by [A. J. Brizard, Phys. Plasmas 11 4429 (2004)], where it was used to eliminate the fast gyromotion from the Fokker-Planck collision operator. The formalism presented here is applicable to the motion of charged particles in planetary magnetic fields as well as in magnetic confinement fusion plasmas, where the corresponding so-called synchrotron radiation can be detected. Applications of the guiding-center radiation-reaction force include tracing of charged particle orbits in complex magnetic fields as well as kinetic description of plasma when the loss of energy and momentum due to radiation plays an important role, e.g., for runaway electron dynamics in tokamaks.

Explore related subjects

physics.plasm-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Eero Hirvijoki, Joan Decker, Alain Brizard, Ola Embréus. 2015-03-26. Guiding-center transformation of the radiation-reaction force in a nonuniform magnetic field. https://doi.org/10.1017/s0022377815000744

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Augmented reality system for visualising magnetic field topology and charged-particle trajectories in magnetic fusion plasmas

A cost-effective augmented reality (AR) system is presented for visualising three-dimensional magnetic field structures and charged-particle trajectories in magnetically confined fusion plasmas. The system presented in this study integrates an orbit-following simulation code with a marker-based AR framework using a web camera and the OpenCV library. By synchronizing the time step of the simulation with the frame rate of the camera, the trajectories are continuously updated and superimposed in real time onto the camera image. Through the interactive operation of manipulating the web camera, users can observe three-dimensional structures, such as magnetic islands, from various positions and viewing angles. Such an AR environment supports an interactive means of exploring three-dimensional spatial structures that can be difficult to interpret from two-dimensional representations alone. It also provides a common visual representation that can be shared through a display by researchers and students with diverse backgrounds in physics, engineering, and related fields. The developed system has been used in practical exercises at the JT-60SA International Fusion School, with exploratory feedback from students.

physics.plasm-ph↗
arXiv2026

Sensitivity of a low-shear heliotron configuration to localised ferrite-steel perturbations

The influence of ferritic steel on low-shear stellarator/heliotron magnetic configurations is investigated for the Heliotron J device using a point dipole magnetisation model. By numerically evaluating ferritic steel plates assumed at several locations inside the Heliotron J vacuum vessel, the changes in the rotational transform and magnetic island width are shown to be sensitive to the installation location. This location sensitivity arises from the toroidal variation of poloidal mode coupling between the background nonaxisymmetric field and ferritic-steel perturbation, rather than being determined solely by the perturbation amplitude. The resulting mode coupling can enhance the resonant vacuum magnetic perturbation at specific locations. Ferritic steel plates placed on the outer side of a straight section produce the most significant changes in the magnetic topology and exhibit the highest sensitivity to violations of the $M=4$ toroidal periodicity. Additionally, we show that appropriate arrangements of passive magnetic dipoles can reduce the effective helical ripple while preserving the vacuum magnetic well depth in Heliotron J, and can induce a stellarator-asymmetric boundary perturbation in low-field experiments.

physics.plasm-ph↗
arXiv2026

Trapping: The "Waterfall" of Vlasov-Poisson Dynamics and the Post-Transient Emergence of Drift-Independent Hole Structures in Collisionless Plasmas

A key aspect of structure formation in collisionless plasmas is particle trapping or, more precisely, the gap this process leaves in the theoretical description. While the dynamics prior to the onset of trapping are governed by Landau physics and phase mixing, the full effects of nonlinearity only emerge during the trapping phase, for which an explicit description is lacking. Consequently, this gap divides the temporal evolution into a linear Vlasov-Poisson phase preceding the transition and a post-transient Vlasov-Poisson phase characterized by a wide spectrum of particle trapping scenarios and associated Schamel equilibria. Metaphorically, this trapping process can thus be compared to a waterfall in fluid dynamics, where, similarly, no explicit dynamic link can be established between the regions above and below the cascade. To resolve this problem of the gap, an analysis using the method of matched asymptotic expansions is proposed. Applied to the singular boundary of the separatrix zone, this approach employs local smoothing techniques, such as those mediated by the two-particle correlation function. It offers a suitable mechanism for selecting hole equilibria in the post-transition phase. Furthermore, we report the existence of a spatially periodic Langmuir hole that vanishes if regularity requirements are too stringent, and we demonstrate that self-acceleration, accompanying the transition from a slow electron acoustic hole to a fast Langmuir hole, is driven by the release of particularly deeply trapped electrons.

physics.plasm-ph↗