Covariant Magnetoionic Theory I: Ray Propagation

Abstract

Accretion onto compact objects plays a central role in high energy astrophysics. In these environments, both general relativistic and plasma effects may have significant impacts upon the propagation of photons. We present a full general relativistic magnetoionic theory, capable of tracing rays in the geometric optics approximation through a magnetised plasma in the vicinity of a compact object. We consider both the cold and warm, ion and pair plasmas. When plasma effects become large the two plasma eignemodes follow different ray trajectories resulting in a large observable polarisation. This has implications for accreting systems ranging from pulsars and X-ray binaries to AGN.