Neutron star magnetospheres: the binary pulsar, Crab and magnetars

TL;DR

This paper reviews evidence that neutron star magnetospheres contain dense plasma on closed field lines, challenging traditional views, and discusses implications for radio and high-energy emissions in various neutron star types.

Contribution

It synthesizes observational and theoretical evidence to propose that dense plasma populates neutron star closed field lines, affecting emission mechanisms across different neutron star classes.

Findings

Dense plasma on closed field lines in neutron stars influences emission.

Magnetar twisting produces dense pair plasma via electric fields.

Magnetic mirroring traps hot particles in long period pulsars.

Abstract

A number of disparate observational and theoretical pieces of evidence indicate that, contrary to the conventional wisdom, neutron stars' closed field lines are populated by dense, hot plasma and may be responsible for producing some radio and high energy emission. This conclusion is based on eclipse modeling of the binary pulsar system PSR J0737-3039A/B (Lyutikov & Thompson 2005), a quantitative theory of Crab giant pulses (Lyutikov 2007) and a number of theoretical works related to production of non-thermal spectra in magnetars through resonant scattering. In magnetars, dense pair plasma is produced by twisting magnetic field lines and associated electric fields required to lift the particles from the surface. In long period pulsars, hot particles on closed field lines can be efficiently trapped by magnetic mirroring, so that relatively low supply rate, e.g. due to a drift from open field lines, may result in high density. In short period pulsars, magnetic mirroring does not work; large densities may still be expected at the magnetic equator near the Y-point.