Axisymmetric pulsar magnetosphere revisited

Abstract

We present a global kinetic plasma simulation of an axisymmetric pulsar magnetosphere with self-consistent $e^{\pm }$ pair production. We use the particle-in-cell method and log-spherical coordinates with a grid size $4096\times 4096$. This allows us to achieve a high voltage induced by the pulsar rotation and investigate pair creation in a young pulsar far from the death line. We find the following. (1) The energy release and $e^{\pm }$ creation are strongly concentrated in the thin, Y-shaped current sheet, with a peak localized in a small volume at the Y-point. (2) The Y-point is shifted inward from the light cylinder by $\sim 15\%$, and "breathes" with a small amplitude. (3) The dense $e^{\pm }$ cloud at the Y-point is in ultra-relativistic rotation, which we call super-rotation, because it exceeds co-rotation with the star. The cloud receives angular momentum flowing from the star along the poloidal magnetic lines. (4) Gamma-ray emission peaks at the Y-point and is collimated in the azimuthal direction, tangent to the Y-point circle. (5) The separatrix current sheet between the closed magnetosphere and the open magnetic field lines is sustained by the electron backflow from the Y-point cloud. Its thickness is self-regulated to marginal charge starvation. (6) Only a small fraction of dissipation occurs in the separatrix inward of the Y-point. A much higher power is released in the equatorial plane, especially at the Y-point where the created dense $e^{\pm }$ plasma is spun up and intermittently ejected through the nozzle between the two open magnetic fluxes.

arXiv comment16 pages, ApJ, in press

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• Scaling up global kinetic models of pulsar magnetospheres using a hybrid force-free-PIC numerical approach
• Synthetic pulsar lightcurves from global kinetic simulations and comparison with the Fermi-LAT catalog
• Listening for Dark Photon Radio from the Galactic Centre
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• Axion signals from neutron star populations
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• Spin-down of a pulsar with a yielding crust
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• Revealing the Unseen: The Discovery of Long-Awaited Radiation from the Intermittent Pulsar PSR B1931+24
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• Axion-Photon Conversion Signals from Neutron Stars with Spacetime Curvature Accounted for in the Magnetosphere Model