Axisymmetric PIC simulations of pulsar magnetospheres with ab initio photon emission and pair production

Global particle-in-cell (PIC) simulations of pulsar magnetospheres performed in recent years comprise a multitude of phenomena, including surface charge injection, general relativity frame dragging corrections to Maxwell’s equations, and QED gamma ray emission and pair production. The QED processes, thought to be critical in the development of pulsar magnetospheric plasmas, are, however, only considered phenomenologically. In this work, we present simulations performed with a recently developed 2D axisymmetric spherical version of the OSIRIS PIC code that treat the photon emission and pair production processes from first principles, leveraging on recent OSIRIS ab initio QED modules.

The spherical code uses a new first-order current deposition scheme that conserves charge to machine precision. Using PIC simulations without QED effects as benchmarks, we apply the new code to study the transition between the charge-separated disk/dome and force-free regimes of magnetic dipoles. The filling of the magnetosphere with plasma and the ability of accelerated particles to initiate pair cascades determines the prevalence of the pulsar phenomenon in neutron star population. We discuss the constraints that our simulations put on the population of radio and gamma-ray emitting pulsars.