The effect of GR and plasma supply on steady-state neutron star magnetospheres*

Magnetospheres of compact objects such as neutron stars and black holes are complex systems where quantum electrodynamic (QED) processes, kinetic-scale pair plasma physics, and general relativity (GR) play an important role. Recent advances in numerical techniques allowed us to perform first-principles simulations of compact neutron star (NS) magnetospheres in curved spacetime. GR effects facilitate pair production in the polar cap via the frame-dragging effect, thus lowering the death line for massive pulsars [e.g. A.Harding et al ApJ 2002]. We explore the coupling between the NS compactness (R_s/R_∗) and the surface plasma supply, and how it modifies the magnetospheric structure. We characterize the spacelike region that forms in the bulk of the polar cap and compare its maximum extension with estimates from previous force-free models [e.g. S.Gralla et al ApJ 2016]. However, when we allow inefficient pair production only in the NS vicinity and limit the plasma supply from the surface, we enter into the "weak pulsar" regime that develops an outer magnetospheric gap. We study this charge-starved solution and discuss its observational implications.