A very general electromagnetic gyrokinetic formalism

TL;DR

This paper develops a comprehensive electromagnetic gyrokinetic formalism that unifies the treatment of plasma fluctuations across multiple scales, accommodating large inhomogeneities and small-scale phenomena within a single theoretical framework.

Contribution

It introduces a general gyrokinetic formalism that does not separate long and short wavelength components, allowing for a unified treatment of plasma dynamics across scales.

Findings

Formalism valid for large inhomogeneities and fluctuations at gyro-scale

Single-field description for all fluctuation scales

Systematic coordinate transformation to remove gyroangle dependence

Abstract

We derive a gyrokinetic formalism which is very generally valid: the ordering allows both large inhomogeneities in plasma flow and magnetic field at long wavelength, like typical drift-kinetic theories, as well as fluctuations at the gyro-scale. The underlying approach is to order the vorticity to be small, and to assert that the timescales in the local plasma frame are long compared to the gyrofrequency. Unlike most other derivations, we do not treat the long and short wavelength components of the fluctuating fields separately; the single-field description defines the particle motion and their interaction with the electromagnetic field at small-scale, the system-scale, and intermediate length scales in a unified fashion. As in earlier literature, the work consists of identifying a coordinate system where the gyroangle-dependent terms are small, and using a near-unity transform to systematically find a set of coordinates where the gyroangle dependence vanishes.