Magnetic Field Evolution in Neutron Stars: One-Dimensional Multi-Fluid Model

Understand

This paper is the first in a series aimed at understanding the long-term evolution of neutron star magnetic fields.

• We model the stellar matter as an electrically neutral and lightly ionized plasma composed of three moving particle species: neutrons, protons, and electrons, which can be converted into each other by weak interactions (beta decays), suffer binary collisions, and be affected by each other's macroscopic electromagnetic fields.
• Since the evolution of the magnetic field occurs over thousands of years or more, compared to dynamical time scales (sound and Alfv\'en) of milliseconds to seconds, we use a slow-motion approximation in which we neglect the inertial terms in the equations of motion for the particles.
• We restrict ourselves to a one-dimensional geometry in which the magnetic field points in one Cartesian direction but varies only along an orthogonal direction.