Work

Guiding-centre Lagrangian and quasi-symmetry

Year: 2025

Type: article

Abstract: A charged particle in a suitably strong magnetic field spirals along the field lines while slowly drifting transversely. This note provides a brief derivation of an effective Lagrangian formulation for the guiding-centre approximation that captures this dynamics without resolving the gyro motion. It also explains how the effective Lagrangian may, for special magnetic fields, admit a ‘quasi-symmetry’ which can give rise to a conserved quantity helpful for plasma confinement in fields lacking a geometric isometry. The aim of this note is to offer a pedagogical introduction and some perspectives on this well-established subject.

Source: Journal of Plasma Physics

DOI: 10.1017/s0022377825000133

Author: Ted Jacobson

Institution: University of Maryland, College Park

Language: English

Topic: Magnetic confinement fusion research

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,550

Funders: National Science Foundation, Government of Canada, Institut Périmètre de physique théorique, Ministry of Colleges and Universities