Dynamo effects in magnetized ideal-plasma cosmologies

TL;DR

This paper analytically studies how magnetic fields influence cosmological perturbations in an anisotropic universe, showing that magnetic induction can grow over time, especially during gravitational condensations.

Contribution

It provides an analytical solution for magnetized cosmological perturbations in anisotropic models, highlighting magnetic field amplification mechanisms.

Findings

Fast-magnetosonic modes are excited perpendicular to the magnetic field.

Magnetic-induction contrast increases at late times.

Gravitational instabilities favor magnetic field amplification.

Abstract

The excitation of cosmological perturbations in an anisotropic cosmological model and in the presence of a homogeneous magnetic field has been studied, using the ideal magnetohydrodynamic (MHD) equations. In this case, the system of partial differential equations which governs the evolution of the magnetized cosmological perturbations can be solved analytically. Our results verify that fast-magnetosonic modes propagating normal to the magnetic field, are excited. But, what's most important, is that, at late times, the magnetic-induction contrast grows, resulting in the enhancement of the ambient magnetic field. This process can be particularly favored by condensations, formed within the plasma fluid due to gravitational instabilities.