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Lagrangian Description of Reduced Magnetohydrodynamics

Yohei KAWAZURA^1,2)

1)

School of Data Science and Management, Utsunomiya University, 350 Minemachi, Utsunomiya, Tochigi 321-8505, Japan

2)

Department of Geophysics, Graduate School of Science, Tohoku University, 6-3 Aoba, Aramaki, Sendai 980-8578, Japan

(Received 9 January 2025 / Accepted 12 February 2025 / Published 23 April 2025)

Abstract

This Letter presents a Lagrangian formulation of reduced magnetohydrodynamics (RMHD) for Alfvénic fluctuations in a uniform background magnetic field. The RMHD equations are derived in Lagrangian coordinates through the least action principle. We also demonstrate that cross helicity conservation is naturally tied to fluid element relabeling symmetry.

Copyright (c) 2025 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

magnetohydrodynamics, lagrangian description, Alfvén waves

DOI: 10.1585/pfr.20.1301025

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