부산대학교 도서관

Aims: Ab initio global particle-in-cell (PIC) simulations of compact neutron star magnetospheres in the align rotator configuration to investigate the role of GR and plasma supply on the polar cap particle acceleration efficiency - precursor of coherent radio emission. Methods: A new module for the PIC code OSIRIS to model plasma dynamics around compact objects with full self-consistent GR effects is presented. A detailed description of the extensions and implementation methods are provided for the main sub-algorithms of the PIC loop, including the field solver, particle pusher and charge-conserving current-deposit scheme. Results: Leptons are efficiently accelerated in the polar caps of neutron stars with force-free magnetospheres. This solution supports strong poloidal currents, which are easily turned to spacelike at any stellar compactness due to the GR frame-dragging effect. Charge-separated magnetospheric solutions, in opposition, depend on the plasma supply and compactness to activate the polar cap. The furthest away the solution is from force-free, the highest the compactness is required for the polar cap activation. Conclusions: GR effects are crucial to explain the pulsar mechanism for low obliquity rotators. Focusing on the aligned rotator, we show that GR relaxes the minimum required poloidal magnetospheric current for the transition of the polar cap to the accelerator regime, thus justifying the observation of weak pulsars beyond the expected death line. Also, we demonstrate how the interplay between the polar cap and outer gaps might explain the intermittent behaviour of the measured spin-down luminosity and the existence of radio sub-pulse nullings for older pulsars.
Comment: 15 pages, 5 figures, 2 tables, submitted to A&A