Theory of pulsar magnetosphere and wind

TL;DR

This paper reviews the fundamental theories of pulsar magnetospheres and winds, discussing models, physical processes, and recent numerical simulations, while highlighting unresolved questions about plasma composition and emission mechanisms.

Contribution

It synthesizes recent theoretical and simulation-based advances in understanding pulsar magnetospheres and winds, emphasizing unresolved issues and observational signatures.

Findings

Recent numerical simulations provide qualitative insights into pulsar magnetospheres.

The composition of magnetospheric plasma remains uncertain, affecting model predictions.

Observational signatures help constrain physical processes in pulsar environments.

Abstract

Neutron stars are fascinating astrophysical objects immersed in strong gravitational and electromagnetic fields, at the edge of our current theories. These stars manifest themselves mostly as pulsars, emitting a timely very stable and regular electromagnetic signal. Even though discovered almost fifty years ago, they still remain mysterious compact stellar objects. In this review, we summarize the most fundamental theoretical aspects of neutron star magnetospheres and winds. The main competing models susceptible to explain their radiative properties like multi-wavelength pulse shapes and spectra and the underlying physical processes such as pair creation and radiation mechanisms are scrutinized. A global but still rather qualitative picture emerges slowly thanks to recent advances in numerical simulations on the largest scales. However considerations about pulsar magnetospheres remain speculative. For instance the exact composition of the magnetospheric plasma is not yet known. Is it solely filled with a mixture of $e^\pm$~leptons, or does it contain a non negligible fraction of protons and/or ions? Actually, is it almost entirely filled or mostly empty except for some small anecdotal plasma filled regions? Answers to these questions will strongly direct the description of the magnetosphere to seemingly contradictory results leading sometimes to inconsistencies. Nevertheless, account are given to the latest developments in the theory of pulsar magnetospheres and winds, the existence of a possible electrosphere and physical insight obtained from related observational signatures of multi-wavelength pulsed emission.