Forward cascade of large-scale primordial magnetic fields during structure formation

TL;DR

This paper investigates how primordial magnetic fields are amplified and evolve during structure formation in the Universe, using semi-analytical models that align with simulation results.

Contribution

It introduces a semi-analytical approach to study the forward cascade of magnetic fields during cosmic structure formation, capturing key spectral evolution features.

Findings

Model reproduces qualitative features of magnetic spectrum evolution

Amplification occurs via adiabatic collapse during structure formation

Semi-analytical results align with cosmological simulations

Abstract

The origin of large scale magnetic fields in the Universe is widely thought to be from early Universe processes, like inflation or phase transitions. These magnetic fields evolve via magnetohydrodynamic processes until the epoch of recombination. When structures begin to form in the later Universe, the conservation of magnetic flux amplifies the magnetic fields via the adiabatic collapse of gravitationally bound gas clouds hosting the magnetic fields and moves them to smaller scales. In this work, we have semi-analytically studied this forward cascade effect, considering simple models of gravitational collapse of structures. We find that this simple model is able to reproduce the general qualitative features of the evolution of the magnetic field spectrum as seen from magnetized cosmological simulations.