Two-fluid model of the pulsar magnetosphere represented as an axisymmetric force-free dipole

TL;DR

This paper develops a self-consistent two-fluid model of the pulsar magnetosphere based on an exact dipolar solution, revealing particle behaviors, potential high-energy emissions near the Y-point, and implications for gap structures.

Contribution

It introduces a novel two-fluid, low-mass, force-free pulsar magnetosphere model incorporating radiation damping and detailed particle dynamics.

Findings

Particles follow magnetic field lines with small azimuthal velocities

Unrestricted Lorentz-factor growth near the Y-point suggests high-energy emissions

The electric field sign change indicates coexistence of polar and outer gaps

Abstract

Based on the exact dipolar solution of the pulsar equation the self-consistent two-fluid model of the pulsar magnetosphere is developed. We concentrate on the low-mass limit of the model, taking into account the radiation damping. As a result, we obtain the particle distributions sustaining the dipolar force-free configuration of the pulsar magnetosphere in case of a slight velocity shear of the electron and positron components. Over most part of the force-free region, the particles follow the poloidal magnetic field lines, with the azimuthal velocities being small. Close to the Y-point, however, the particle motion is chiefly azimuthal and the Lorentz-factor grows unrestrictedly. This may result in the very-high-energy emission from the vicinity of the Y-point and may also imply the magnetocentrifugal formation of a jet. As for the first-order quantities, the longitudinal accelerating electric field is found to change the sign, hinting at coexistence of the polar and outer gaps. Besides that, the components of the plasma conductivity tensor are derived and the low-mass analogue of the pulsar equation is formulated as well.