On the singularity of Lie-transform perturbation approach to the guiding-center problem

TL;DR

This paper introduces a new Lie-transform perturbation scheme for guiding-center motion that directly addresses the intrinsic singularity problem, producing gauge functions explicitly and unifying effects of strong ExB shearing and electromagnetic fluctuations.

Contribution

A novel Lie-transform perturbation method that naturally resolves singularities and explicitly determines gauge functions in guiding-center transformations.

Findings

Explicit gauge functions derived via integral over gyro-angle

Unified formalism incorporating ExB shearing and electromagnetic fluctuations

Addresses intrinsic singularity in Lie-transform perturbation

Abstract

We present a novel scheme of carrying out the Lie-transform perturbation for the guiding-center motion, with an aim at addressing directly the problem of singularity which exists intrinsically in the determining equation for the generating vector, and which gives rise to the formidable gauge functions in the pure oscillating part of the Lie transformation. Whereas in most applications of Lie-transform perturbation such gauge functions must be approximately solved from some partial differential equations, our scheme, characterized by a staggered determination of the generating vectors, naturally produces the gauge functions through explicit integral over the gyro-angle, leaving no unaccountable error of high order in all the succeeding transformations. Based on such scheme, a formalism of guiding-center transformation has been derived in a unified manner retaining the effects of the strong ExB shearing as well as those of electromagnetic fluctuations.