Generalized covariant gyrokinetic dynamics of magnetoplasmas

TL;DR

This paper develops a generalized covariant gyrokinetic theory for relativistic magnetoplasmas, incorporating nonlinear perturbations and ensuring physical realizability, to better describe particle dynamics near massive astrophysical objects.

Contribution

It formulates a new gyrokinetic theory based on a synchronous variational principle that accurately accounts for nonlinear gravitational and electromagnetic perturbations.

Findings

Includes treatment of nonlinear perturbations in gyrokinetic dynamics.

Ensures validity for large and vanishing parallel electric fields.

Introduces four-velocity corrections for intense magnetic fields.

Abstract

A basic prerequisite for the investigation of relativistic astrophysical magnetoplasmas, occurring typically in the vicinity of massive stellar objects (black holes, neutron stars, active galactic nuclei, etc.), is the accurate description of single-particle covariant dynamics, based on gyrokinetic theory (Beklemishev et al.,1999-2005). Provided radiation-reaction effects are negligible, this is usually based on the assumption that both the space-time metric and the EM fields (in particular the magnetic field) are suitably prescribed and are considered independent of single-particle dynamics, while allowing for the possible presence of gravitational/EM perturbations driven by plasma collective interactions which may naturally arise in such systems. The purpose of this work is the formulation of a generalized gyrokinetic theory based on the synchronous variational principle recently pointed out (Tessarotto et al., 2007) which permits to satisfy exactly the physical realizability condition for the four-velocity. The theory here developed includes the treatment of nonlinear perturbations (gravitational and/or EM) characterized locally, i.e., in the rest frame of a test particle, by short wavelength and high frequency. Basic feature of the approach is to ensure the validity of the theory both for large and vanishing parallel electric field. It is shown that the correct treatment of EM perturbations occurring in the presence of an intense background magnetic field generally implies the appearance of appropriate four-velocity corrections, which are essential for the description of single-particle gyrokinetic dynamics.