Fermi Gamma-ray Space Telescope

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

Fabio Cruz
(A. Chen, A. Spitkovsky, T. Grismayer, L. O. Silva)


Global particle-in-cell (PIC) simulations provide an important insight about the connection between small and large-scale phenomena in pulsar magnetospheres. Previous works on global PIC simulations of pulsars have used artificial models for pair creation, but the filling of the magnetosphere depends on the details of these models. In this work, we present PIC simulations of aligned pulsar magnetospheres performed with a recently developed 2D axisymmetric spherical version of the OSIRIS PIC code that treat the Quantum Electrodynamics (QED) processes of photon emission and pair production from first principles. These simulations use recent ab initio QED modules in OSIRIS, as well as a new first-order current deposition scheme that conserves charge to machine precision, and are used to understand the role of pair cascades in the pulsar magnetosphere macroscopic shape. Using PIC simulations with artificial 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.