Dynamics of magnetospheres of rotating compact objects with General Relativity

Rotating compact objects are known to fuel the most energetic extreme astrophysical phenomena in the universe. Their rotation induces an external electric field capable of efficiently accelerating particles, populating the magnetosphere with e± plasma through quantum electrodynamics (QED) processes and giving rise to the observed coherent and incoherent radiation.

It is only possible to understand these first-principles phenomena using particle-in-cell (PIC) kinetic simulations of the global magnetosphere, capturing magnetospheric current closure, QED processes, and general relativity (GR). In this Thesis, we have generalized the advanced PIC code OSIRIS to arbitrary curvilinear orthogonal coordinates, suitable for modeling plasma dynamics in magnetospheres of compact objects, i.e. with significant spacetime curvature. The implementation detailed in this thesis extends the applicability of this tool beyond astrophysical scenarios. In particular, to laboratory settings in more complicated geometries.

We ran massively parallel simulations of pulsar magnetospheres, performing numerical experiments to understand the role of general relativity and plasma supply in the radio beam generation phase for low obliquity rotators. The results show that GR is fundamental to the appearance of the radio beam in the first place for aligned rotators.

For older stars, it can even distinguish a pulsar from a neutron star. In this thesis, we also explored the effect of GR when the polar gap is in a non-stationary regime, characterized by having an (almost) vacuum gap at the base of the set of open magnetic field lines. Under these conditions, the polar discharge occurs through a succession of isolated plasma filaments that do not follow the stellar rotation, usually used to explain drifting components of the beam.

The results demonstrate the appearance of a new plasma filament, giving a natural explanation for the more bi-cone core emission configuration that agrees with the observations.