On the Global Structure of Pulsar Force-free Magnetosphere

TL;DR

This paper revises boundary conditions in the pulsar equation to better model the force-free magnetosphere, introducing a generalized multipolar solution that improves understanding of the magnetic field structure at large distances.

Contribution

It proposes a new framework for the pulsar magnetosphere by incorporating plasma-producing gaps and deriving a generalized multipolar solution to the pulsar equation.

Findings

Generalized multipolar solution better represents dipolar fields at large distances

Outer gap location inside the light cylinder affects the alignment of null and critical lines

Framework sets stage for further analytic and numerical studies of pulsar magnetospheres

Abstract

The dipolar magnetic field structure of the neutron star is modified by the plasma originating in the pulsar magnetopshere. In the simplest case of a stationary axisymmetric force-free magnetosphere, a self-consistent description of the fields and currents is given by the well-known pulsar equation. Here we revise the commonly used boundary conditions of the problem in order to incorporate the plasma-producing gaps and to provide a framework for a truly self-consistent treatment of the pulsar magnetosphere. The generalized multipolar solution of the pulsar equation is found, which, as compared to the customary split monopole solution, is suggested to better represent the character of the dipolar force-free field at large distances. In particular, the outer gap location entirely inside the light cylinder implies that beyond the light cylinder the null and critical lines should be aligned and go parallel to the equator at a certain altitude. Our scheme of the pulsar force-free magnetosphere, which will hopefully be followed by extensive analytic and numerical studies, may have numerous implications for different fields of pulsar research.