# Gauge-free electromagnetic gyrokinetic theory

## TL;DR

This paper introduces a gauge-free electromagnetic gyrokinetic theory that reformulates gyrocenter equations using electromagnetic fields directly, simplifying the modeling of plasma dynamics.

## Contribution

It develops a novel gauge-free formulation of gyrokinetics, explicitly deriving polarization and magnetization from the Hamiltonian, suitable for simulations and hybrid models.

## Key findings

- Derived gyrocenter polarization and magnetization explicitly.
- Presented source expressions compatible with simulation.
- Reformulated equations in terms of electromagnetic fields.

## Abstract

A new gauge-free electromagnetic gyrokinetic theory is developed, in which the gyrocenter equations of motion and the gyrocenter phase-space transformation are expressed in terms of the perturbed electromagnetic fields, instead of the usual perturbed potentials. Gyrocenter polarization and magnetization are derived explicitly from the gyrocenter Hamiltonian, up to first order in the gyrocenter perturbation expansion. Expressions for the sources in Maxwell's equations are derived in a form that is suitable for simulation studies, as well as kinetic-gyrokinetic hybrid modeling.