Covariant formulation of spatially nonsymmetric kinetic equilibria in magnetized astrophysical plasmas
Abstract
Astrophysical plasmas in the surrounding of compact objects and subject to intense gravitational and electromagnetic fields are believed to give rise to relativistic regimes. Theoretical and observational evidences suggest that magnetized plasmas of this type are collisionless and can persist for long times (e.g., with respect to a distant observer, coordinate, time), while exhibiting geometrical structures characterized by the absence of welldefined spatial symmetries. In this paper, the problem is posed whether such configurations can correspond to some kind of kinetic equilibrium. The issue is addressed from a theoretical perspective in the framework of a covariant Vlasov statistical description, which relies on the method of invariants. For this purpose, a systematic covariant variational formulation of gyrokinetic theory is developed, which holds without requiring any symmetry condition on the background fields. As a result, an asymptotic representation of the relativistic particle magnetic moment is obtained from its formal exact solution, in terms of a suitably defined invariant series expansion parameter (perturbative representation). On such a basis, it is shown that spatially nonsymmetric kinetic equilibria can actually be determined, an example being provided by Gaussianlike distributions. As an application, the physical mechanisms related to the occurrence of a nonvanishing equilibrium fluid 4flow are investigated.
 Publication:

Physics of Plasmas
 Pub Date:
 May 2014
 DOI:
 10.1063/1.4874324
 Bibcode:
 2014PhPl...21e2901C