Particle-in-cell simulations of pulsar magnetospheres: transition between electrosphere and force-free regimes

TL;DR

This paper uses advanced particle-in-cell simulations to explore how pulsar magnetospheres transition between electrosphere and force-free states, introducing new code extensions and analyzing different plasma injection methods.

Contribution

It presents a new extension of the OSIRIS PIC code for axisymmetric pulsar magnetosphere modeling and systematically compares plasma injection schemes.

Findings

Active solutions depend on plasma injection rates and methods.

Pair production schemes require specific energy scale separations.

Charge-conserving current deposition scheme improves simulation accuracy.

Abstract

Global particle-in-cell (PIC) simulations of pulsar magnetospheres are performed with a volume, surface and pair production-based plasma injection schemes to systematically investigate the transition between electrosphere and force-free pulsar magnetospheric regimes. A new extension of the PIC code OSIRIS to model pulsar magnetospheres using a two-dimensional axisymmetric spherical grid is presented. The sub-algorithms of the code and thorough benchmarks are presented in detail, including a new first-order current deposition scheme that conserves charge to machine precision. It is shown that all plasma injection schemes produce a range of magnetospheric regimes. Active solutions can be obtained with surface and volume injection schemes when using artificially large plasma injection rates, and with pair production-based plasma injection for sufficiently large separation between kinematic and pair production energy scales.